[FIR] Fix missing USELESS_CAST

`FirUselessTypeOperationCallChecker` always checks exact types matching for `as` operator

Simplify code of cast checker and utils

^KT-56629 Fixed
^KT-56615 Fixed
^KT-59820 Fixed

compiler/fir/analysis-tests/testData/resolve/checkers/redundantNullCheckOnAsCast.kt

@@ -2,7 +2,7 @@
 
 fun test_1(a: Any?) {
     (a as String?)!!
-    (a as? String)!!
+    (a <!USELESS_CAST!>as? String<!>)!!
 }
 
 fun test_2(a: Any?) {

compiler/fir/analysis-tests/testData/resolveWithStdlib/problems/capturedTypeInEquality.kt

@@ -14,7 +14,7 @@ interface FirTarget<E : FirTargetElement> {
 
 fun foo(target: FirTarget<FirFunction<*>>, property: FirProperty) {
     val functionTarget = target.labeledElement
-    val x = (functionTarget as? FirFunction)?.let {
+    val x = (functionTarget <!USELESS_CAST!>as? FirFunction<!>)?.let {
         if (property.getter === functionTarget) {
             return@let 1
         }