[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/testData/diagnostics/tests/generics/capturedParameters/uncheckedCast.fir.kt

@@ -37,7 +37,7 @@ fun <E> foo(x: Any, y: Any) : Any {
     y <!UNCHECKED_CAST!>as Outer<*><!>
     y as <!NO_TYPE_ARGUMENTS_ON_RHS!>Outer<!>
 
-    y <!UNCHECKED_CAST!>as Outer<*>.Inner<!>
+    y <!CAST_NEVER_SUCCEEDS!>as<!> Outer<*>.Inner
     y as <!NO_TYPE_ARGUMENTS_ON_RHS!>Outer.Inner<!>
 
     return C()