[android] improve performance of Entry.MaxLength

Context: dotnet#10713

When investigating a customer sample:

* Navigate from a Shell flyout

* To a new page with several `Entry` controls

When profiling on a Pixel 5, it seems one hot path is `Entry.MaxLength`:

    18.52ms (0.22%) microsoft.maui!Microsoft.Maui.Platform.EditTextExtensions.UpdateMaxLength(Android.Widget.EditText,Microsoft.Maui.IEntry)
    16.03ms (0.19%) microsoft.maui!Microsoft.Maui.Platform.EditTextExtensions.UpdateMaxLength(Android.Widget.EditText,int)
    12.16ms (0.14%) microsoft.maui!Microsoft.Maui.Platform.EditTextExtensions.SetLengthFilter(Android.Widget.EditText,int)

* `EditTextExtensions.UpdateMaxLength()` calls
    * `EditText.Text` getter and setter
    * `EditTextExtensions.SetLengthFilter()` calls
        * `EditText.Get/SetFilters()`

What happens is we end up marshaling strings and `IInputFilter[]` back
and forth between C# and Java for every `Entry` on the page.

This seems like a prime candidate to move code from C# to Java. I
tried to just port the code as-is without changing logic -- so we
*should* get the exact same behavior as before.

Since all `Entry`s go through this code path (even ones with a default
value for `MaxLength`), this improves the performance of all `Entry`
and `SearchBar` on Android. With these changes in place, the calls to
`EditTextExtensions.UpdateMaxLength()` are now so fast they are
missing from the trace now, saving ~19ms when navigating to this page.

One note, is I found this was the recommended way to create a mutable
`List<T>` from an array in Java:

    List<InputFilter> currentFilters = new ArrayList<>(Arrays.asList(editText.getFilters()));

https://stackoverflow.com/a/11659198

Makes me appreciate C#! :)

src/Controls/tests/DeviceTests/Elements/Entry/EntryTests.cs

@@ -32,6 +32,26 @@ public async Task TextTransformUpdated(string text, TextTransform transform, str
 			Assert.Equal(expected, platformText);
 		}
 
+		[Fact]
+		public async Task MaxLengthTrims()
+		{
+			var entry = new Entry
+			{
+				Text = "This is text",
+			};
+
+			await InvokeOnMainThreadAsync(async () =>
+			{
+				var handler = CreateHandler<EntryHandler>(entry);
+
+				entry.MaxLength = 4;
+				Assert.Equal("This", entry.Text);
+
+				var platformText = await GetPlatformText(handler);
+				Assert.Equal("This", platformText);
+			});
+		}
+
 #if WINDOWS
 		// Only Windows needs the IsReadOnly workaround for MaxLength==0 to prevent text from being entered
 		[Fact]

src/Core/AndroidNative/maui/src/main/java/com/microsoft/maui/PlatformInterop.java

@@ -12,11 +12,14 @@
 import android.graphics.drawable.PaintDrawable;
 import android.net.Uri;
 import android.os.Build;
+import android.text.Editable;
+import android.text.InputFilter;
 import android.util.TypedValue;
 import android.view.Gravity;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewParent;
+import android.widget.EditText;
 import android.widget.FrameLayout;
 import android.widget.ImageView;
 import android.widget.LinearLayout;
@@ -47,6 +50,9 @@
 
 import java.io.InputStream;
 import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 
 public class PlatformInterop {
     public static void requestLayoutIfNeeded(View view) {
@@ -455,6 +461,53 @@ private static boolean isColorType(TypedValue value)
         }
     }
 
+    /**
+     * Sets the maxLength of an EditText
+     * @param editText
+     * @param maxLength
+     */
+    public static void updateMaxLength(@NonNull EditText editText, int maxLength)
+    {
+        setLengthFilter(editText, maxLength);
+
+        Editable currentText = editText.getText();
+        if (currentText.length() > maxLength)
+        {
+            editText.setText(currentText.subSequence(0, maxLength));
+        }
+    }
+
+    /**
+     * Updates the InputFilter[] of an EditText. Used for Entry and SearchBar.
+     * @param editText
+     * @param maxLength
+     */
+    public static void setLengthFilter(@NonNull EditText editText, int maxLength)
+    {
+        if (maxLength == -1)
+            maxLength = Integer.MAX_VALUE;
+
+        List<InputFilter> currentFilters = new ArrayList<>(Arrays.asList(editText.getFilters()));
+        boolean changed = false;
+        for (int i = 0; i < currentFilters.size(); i++) {
+            InputFilter filter = currentFilters.get(i);
+            if (filter instanceof InputFilter.LengthFilter) {
+                currentFilters.remove(i);
+                changed = true;
+                break;
+            }
+        }
+
+        if (maxLength >= 0) {
+            currentFilters.add(new InputFilter.LengthFilter(maxLength));
+            changed = true;
+        }
+        if (changed) {
+            InputFilter[] newFilter = new InputFilter[currentFilters.size()];
+            editText.setFilters(currentFilters.toArray(newFilter));
+        }
+    }
+
     private static class ColorStates
     {
         static final int[] EMPTY = new int[] { };

src/Core/src/Platform/Android/EditTextExtensions.cs

@@ -82,42 +82,11 @@ public static void UpdateMaxLength(this EditText editText, IEntry entry) =>
 		public static void UpdateMaxLength(this EditText editText, IEditor editor) =>
 			UpdateMaxLength(editText, editor.MaxLength);
 
-		public static void UpdateMaxLength(this EditText editText, int maxLength)
-		{
-			editText.SetLengthFilter(maxLength);
-
-			var newText = editText.Text.TrimToMaxLength(maxLength);
-			if (editText.Text != newText)
-				editText.Text = newText;
-		}
-
-		public static void SetLengthFilter(this EditText editText, int maxLength)
-		{
-			if (maxLength == -1)
-				maxLength = int.MaxValue;
-
-			var currentFilters = new List<IInputFilter>(editText.GetFilters() ?? new IInputFilter[0]);
-			var changed = false;
+		public static void UpdateMaxLength(this EditText editText, int maxLength) =>
+			PlatformInterop.UpdateMaxLength(editText, maxLength);
 
-			for (var i = 0; i < currentFilters.Count; i++)
-			{
-				if (currentFilters[i] is InputFilterLengthFilter)
-				{
-					currentFilters.RemoveAt(i);
-					changed = true;
-					break;
-				}
-			}
-
-			if (maxLength >= 0)
-			{
-				currentFilters.Add(new InputFilterLengthFilter(maxLength));
-				changed = true;
-			}
-
-			if (changed)
-				editText.SetFilters(currentFilters.ToArray());
-		}
+		public static void SetLengthFilter(this EditText editText, int maxLength) =>
+			PlatformInterop.SetLengthFilter(editText, maxLength);
 
 		public static void UpdatePlaceholder(this EditText editText, IPlaceholder textInput)
 		{