Enable unreachable_from_main linter rule (#4586)

* Enable 'unreachable_from_main' linter rule

* Remove old debugging function too

* Sort linter rules

analysis_options.yaml

@@ -79,6 +79,7 @@ linter:
     - unnecessary_null_checks
     - unnecessary_parenthesis
     - unnecessary_statements
+    - unreachable_from_main
     - use_if_null_to_convert_nulls_to_bools
     - use_late_for_private_fields_and_variables
     - use_setters_to_change_properties

test/rule_test.dart

@@ -179,17 +179,6 @@ void defineRuleUnitTests() {
   });
 }
 
-/// Handy for debugging.
-void defineSoloRuleTest(String ruleToTest) {
-  for (var entry in Directory(ruleTestDataDir).listSync()) {
-    if (entry is! File || !isDartFile(entry)) continue;
-    var ruleName = p.basenameWithoutExtension(entry.path);
-    if (ruleName == ruleToTest) {
-      testRule(ruleName, entry);
-    }
-  }
-}
-
 void testRule(String ruleName, File file,
     {bool debug = true,
     bool failOnErrors = true,

tool/scorecard.dart

@@ -193,10 +193,6 @@ class ScoreCard {
     scores.forEach(f);
   }
 
-  void removeWhere(bool Function(LintScore element) test) {
-    scores.removeWhere(test);
-  }
-
   static Future<ScoreCard> calculate() async {
     var lintsWithFixes = await _getLintsWithFixes();
     var lintsWithAssists = await _getLintsWithAssists();