[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/inference/dontThrowEmptyIntersectionException.fir.kt

@@ -15,7 +15,7 @@ public interface I<K> {}
 // FILE: main.kt
 fun main(z: I<String>) {
     z <!UNCHECKED_CAST!>as Test<Test2<Int, *>><!>
-    z <!UNCHECKED_CAST!>as Test<Test2<Int, <!UNRESOLVED_REFERENCE!>Foo<!>>><!>
+    z as Test<Test2<Int, <!UNRESOLVED_REFERENCE!>Foo<!>>>
     z as Test<<!UNRESOLVED_REFERENCE!>Foo<!>>
     z as <!UNRESOLVED_REFERENCE!>Any2<!>
     println(z)