[FIR] Report all Visibilities.Unknown in FirOverrideChecker

Check all members for `Visibility.Unknown`,
otherwise we miss them when they come
from supertypes. This is the reason why
the FP intellij build failed with a
cryptic stacktrace instead of a
human-readable diagnostic.

Also, do report the diagnostic at all
cases of `Visibilities.Unknown`. Turns
out, there are no "simple to reason
about" situations here :(

Also, an interesting detail:
`retrieveDirectOverriddenOf` returns an
empty list for intersection overrides.
But this doesn't seem to break anything...

Replacing `CANNOT_INFER_VISIBILITY`'s
type `KtDeclaration` with
`PsiNameIdentifierOwner` and the related
changes in `PositioningStrategies`
were needed to prevent an exception saying that
`PsiClassImpl` is not a subtype of
`KtDeclaration`.

compiler/fir/analysis-tests/testData/resolve/incorrectSuperCall.kt

@@ -11,7 +11,7 @@ open class B {
     open fun baz() {}
 }
 
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B() {
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B() {
     override fun foo() {
         super.foo()