[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/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.checkers.generator.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.builtins.functions.FunctionTypeKind
@@ -926,7 +927,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirCallableSymbol<*>>("overridden")
             parameter<Name>("containingClassName")
         }
-        val CANNOT_INFER_VISIBILITY by error<KtDeclaration>(PositioningStrategy.DECLARATION_NAME) {
+        val CANNOT_INFER_VISIBILITY by error<PsiNameIdentifierOwner>(PositioningStrategy.DECLARATION_NAME) {
             parameter<FirCallableSymbol<*>>("callable")
         }