[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/testData/diagnostics/tests/multiplatform/scopes/manyImplMemberNotImplemented.fir.kt

@@ -10,8 +10,8 @@
 expect open class C1()
 expect interface I1
 
-open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_1<!> : C1(), I1
-open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_2<!> : I1, C1()
+open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_1<!> : C1(), I1
+open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_2<!> : I1, C1()
 
 expect open class Expect1_1 : C1, I1
 expect open class Expect1_2 : I1, C1
@@ -37,8 +37,8 @@ actual interface I1 {
     fun f() {}
 }
 
-actual open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_1<!> : C1(), I1
-actual open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_2<!> : I1, C1()
+actual open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_1<!> : C1(), I1
+actual open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_2<!> : I1, C1()
 
 
 actual abstract class C2 actual constructor() {

compiler/testData/diagnostics/tests/multiplatform/scopes/manyInterfacesMemberNotImplemented.fir.kt

@@ -11,9 +11,9 @@
 expect interface S1
 expect interface S2
 
-open <!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class A<!> : S1, S2
+open <!CANNOT_INFER_VISIBILITY, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class A<!> : S1, S2
 
-class B : A()
+<!CANNOT_INFER_VISIBILITY!>class B<!> : A()
 
 // MODULE: jvm()()(common)
 // TARGET_PLATFORM: JVM