Fix CCE in generated code that happens when comparing boxed chars

The problem was that when obtaining char from the wrapper,
codegen used int as expected type that led
to a ClassCastException: java.lang.Character cannot be cast to java.lang.Number

The solution is using coercion to chars, it's still correct,
because of implicit widening coercion in JVM from C to I

 #KT-15105 Fixed

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

@@ -785,6 +785,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("compareBoxedChars.kt")
+        public void testCompareBoxedChars() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/binaryOp/compareBoxedChars.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("compareWithBoxedDouble.kt")
         public void testCompareWithBoxedDouble() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/binaryOp/compareWithBoxedDouble.kt");