[FIR] Utilize equality compatibility logic for cast checks

This makes it more consistent and fixes some
overlooked corner cases. Also it was decided
on the last equality applicability DM
(KT-62646) that we'd like
`is`/`!is`/`as`/`as?` to work similarly
to `===`/`!==`.

Also note that it now gives a clearer
explaination of why some corner cases work
the way they do. For example,
`FirPsiDiagnosticTestGenerated.testLambdaInLhsOfTypeOperatorCall`
yields `UNCHECKED_CAST` instead of
`CAST_NEVER_SUCCEEDS`, because
`toTypeInfo()` replaces all type arguments
with star projections, even when the argument
is not a type parameter. This is because
it has been desided to work this way in
KT-57779.

In
`FirPsiOldFrontendDiagnosticsTestGenerated..NeverSucceeds#testNoGenericsRelated`
the diagnostic is introduced, because
`t2 as FC1` and `FC1` is a final class with
no `T5` supertype.

`UNCHECKED_CAST` in
`FirPsiOldFrontendDiagnosticsTestGenerated.testSmartCast`
disappeared, because previously we didn't
take smartcasts into account.

Note that
`FirPsiOldFrontendDiagnosticsTestGenerated.testMappedSubtypes`
is a false positive. It appears because `isSubtypeOf()` doesn't
take into account platform types in supertypes of the given types
(doesn't map them).

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/32.fir.kt

@@ -44,7 +44,7 @@ fun case_2(x: Int?, y: Nothing?) {
  */
 fun case_3(x: Int?) {
     if (x == null) {
-        x as Int
+        x <!CAST_NEVER_SUCCEEDS!>as<!> Int
         stringArg(<!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Nothing")!>x<!>)
         <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int? & kotlin.Nothing")!>x<!>
     }

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/34.fir.kt

@@ -124,7 +124,7 @@ fun case_10() {
     do {
         x = null
         break
-    } while ((x as String).length > 1)
+    } while ((x <!CAST_NEVER_SUCCEEDS!>as<!> String).length > 1)
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String? & kotlin.Nothing?")!>x<!>
     <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String? & kotlin.Nothing?")!>x<!><!UNSAFE_CALL!>.<!>length
 }