Reverts #40684 (#41009)

We're reverting because Elastic Agent CI has been failing and we've narrowed it down to the type assertion failing here and not checking `ok` right after: https://github.com/elastic/beats/blob/138e43cad7eda93c1414641682056b6c88efcf1d/winlogbeat/sys/strings_windows.go#L31-L32

Specifically, when integration tests for Elastic Agent run on its CI Windows hosts, we are seeing this failure in the log:

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xc0000005 code=0x0 addr=0x0 pc=0x284f4bf]

goroutine 1 [running]:
golang.org/x/text/encoding/charmap.(*Charmap).ID(0x0)
        /go/pkg/mod/golang.org/x/[email protected]/encoding/charmap/charmap.go:111 +0x1f
github.com/elastic/beats/v7/winlogbeat/sys.init.0()
        /go/src/github.com/elastic/beats/winlogbeat/sys/strings_windows.go:32 +0x10c
```

CHANGELOG.next.asciidoc

@@ -363,8 +363,6 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 
 *Winlogbeat*
 
-- Add handling for missing `EvtVarType`s in experimental api. {issue}19337[19337] {pull}40684[40684]
-
 
 *Functionbeat*
 

winlogbeat/sys/strings.go

@@ -44,27 +44,3 @@ func RemoveWindowsLineEndings(s string) string {
 	s = strings.Replace(s, "\r\n", "\n", -1)
 	return strings.TrimRight(s, "\n")
 }
-
-// BinaryToString converts a binary field which is encoded in hexadecimal
-// to its string representation. This is equivalent to hex.EncodeToString
-// but its output is in uppercase to be equivalent to the windows
-// XML formatting of this fields.
-func BinaryToString(bin []byte) string {
-	if len(bin) == 0 {
-		return ""
-	}
-
-	const hexTable = "0123456789ABCDEF"
-
-	size := len(bin) * 2
-	buffer := make([]byte, size)
-
-	j := 0
-	for _, v := range bin {
-		buffer[j] = hexTable[v>>4]
-		buffer[j+1] = hexTable[v&0x0f]
-		j += 2
-	}
-
-	return string(buffer)
-}

winlogbeat/sys/strings_test.go

@@ -36,12 +36,6 @@ func TestUTF16BytesToString(t *testing.T) {
 	assert.Equal(t, input, output)
 }
 
-func TestMakeDisplayableBinaryString(t *testing.T) {
-	input := []byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF}
-	output := BinaryToString(input)
-	assert.Equal(t, "0123456789ABCDEF", output)
-}
-
 func BenchmarkUTF16BytesToString(b *testing.B) {
 	utf16Bytes := common.StringToUTF16Bytes("A logon was attempted using explicit credentials.")
 

winlogbeat/sys/wineventlog/syscall_windows.go

@@ -442,16 +442,11 @@ func (v EvtVariant) Data(buf []byte) (interface{}, error) {
 	switch typ {
 	case EvtVarTypeNull:
 		return nil, nil
-	case EvtVarTypeString, EvtVarTypeEvtXml:
+	case EvtVarTypeString:
 		addr := unsafe.Pointer(&buf[0])
 		offset := v.ValueAsUintPtr() - uintptr(addr)
 		s, err := sys.UTF16BytesToString(buf[offset:])
 		return s, err
-	case EvtVarTypeAnsiString:
-		addr := unsafe.Pointer(&buf[0])
-		offset := v.ValueAsUintPtr() - uintptr(addr)
-		s, err := sys.ANSIBytesToString(buf[offset:])
-		return s, err
 	case EvtVarTypeSByte:
 		return int8(v.ValueAsUint8()), nil
 	case EvtVarTypeByte:
@@ -481,28 +476,15 @@ func (v EvtVariant) Data(buf []byte) (interface{}, error) {
 			return false, nil
 		}
 		return true, nil
-	case EvtVarTypeBinary:
-		addr := unsafe.Pointer(&buf[0])
-		offset := v.ValueAsUintPtr() - uintptr(addr)
-		return sys.BinaryToString(buf[offset:]), nil
 	case EvtVarTypeGuid:
 		addr := unsafe.Pointer(&buf[0])
 		offset := v.ValueAsUintPtr() - uintptr(addr)
 		guid := (*windows.GUID)(unsafe.Pointer(&buf[offset]))
 		copy := *guid
 		return copy, nil
-	case EvtVarTypeSizeT:
-		return v.ValueAsUintPtr(), nil
 	case EvtVarTypeFileTime:
 		ft := (*windows.Filetime)(unsafe.Pointer(&v.Value))
 		return time.Unix(0, ft.Nanoseconds()).UTC(), nil
-	case EvtVarTypeSysTime:
-		st := (*windows.Systemtime)(unsafe.Pointer(&v.Value))
-		var ft windows.Filetime
-		if err := sys.SystemTimeToFileTime(st, &ft); err != nil {
-			return nil, err
-		}
-		return time.Unix(0, ft.Nanoseconds()).UTC(), nil
 	case EvtVarTypeSid:
 		addr := unsafe.Pointer(&buf[0])
 		offset := v.ValueAsUintPtr() - uintptr(addr)