[FIR] Run FirOverrideChecker for fake overrides

The change in
`FirOptInUsageBaseChecker` is needed
to prevent `OPT_IN_OVERRIDE` on
intersection overrides where one
of the base functions requires opt-in.
We never designed this in such
a way that it's an error.
See:
`FirPsiOldFrontendDiagnosticsTestGenerated.testIncorrectTargetsForExperimentalAnnotation`.

According to KT-63741, the case like
`kt40510.fir.kt` should, in fact,
be an error. It will be addressed
separately.

compiler/testData/diagnostics/tests/delegation/kt40510.fir.kt

@@ -11,4 +11,4 @@ public abstract class A {
 // FILE: main.kt
 import foo.A
 
-class DelegatedA(val a: A) : <!DELEGATION_NOT_TO_INTERFACE, SUPERTYPE_NOT_INITIALIZED!>A<!> by a
+class <!CANNOT_OVERRIDE_INVISIBLE_MEMBER!>DelegatedA<!>(val a: A) : <!DELEGATION_NOT_TO_INTERFACE, SUPERTYPE_NOT_INITIALIZED!>A<!> by a