[IR] Fix issue getting the length property from CharSequence bounded type parameter

Use the class of the subtype of CharSequence when available. When
it is not (for type parameters bounded by CharSequence) call the
CharSequence getter and 'get' method. Using the most specific type
posible fixes the forInStringSpecialized test that expects the
use of INVOKEVIRTUAL and not INVOKEINTERFACE.

Add tests for the type parameter use.

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1677,6 +1677,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             runTest("compiler/testData/codegen/bytecodeText/forLoop/forInCharSequence.kt");
         }
 
+        @TestMetadata("forInCharSequenceTypeParameter.kt")
+        public void testForInCharSequenceTypeParameter() throws Exception {
+            runTest("compiler/testData/codegen/bytecodeText/forLoop/forInCharSequenceTypeParameter.kt");
+        }
+
         @TestMetadata("forInDownToCharMinValue.kt")
         public void testForInDownToCharMinValue() throws Exception {
             runTest("compiler/testData/codegen/bytecodeText/forLoop/forInDownToCharMinValue.kt");
@@ -1890,6 +1895,11 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
                 runTest("compiler/testData/codegen/bytecodeText/forLoop/forInIndices/forInCharSequenceIndices.kt");
             }
 
+            @TestMetadata("forInCharSequenceTypeParameterIndices.kt")
+            public void testForInCharSequenceTypeParameterIndices() throws Exception {
+                runTest("compiler/testData/codegen/bytecodeText/forLoop/forInIndices/forInCharSequenceTypeParameterIndices.kt");
+            }
+
             @TestMetadata("forInCollectionImplicitReceiverIndices.kt")
             public void testForInCollectionImplicitReceiverIndices() throws Exception {
                 runTest("compiler/testData/codegen/bytecodeText/forLoop/forInIndices/forInCollectionImplicitReceiverIndices.kt");