[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/testData/diagnostics/tests/smartCasts/castchecks/variables.fir.kt

@@ -60,7 +60,7 @@ fun f(a: SomeClass?) {
         // 'c' can be cast to SomeSubClass
         aa.hashCode()
         aa.foo
-        (aa as? SomeSubClass)<!UNSAFE_CALL!>.<!>foo
+        (aa <!USELESS_CAST!>as? SomeSubClass<!>)<!UNSAFE_CALL!>.<!>foo
         c.hashCode()
         c.foo
     }