[FIR] Set status.isOverride for fake overrides

Even though SO may not be correct
overrides sometimes, it feels more
natural to treat fake overrides as...
well, "overrides". And without it
we'd need to make the code in
`FirOverrideChecker` less intuitive.

analysis/analysis-api/testData/components/scopeProvider/scopeContextForPosition/enumEntry.txt

@@ -192,7 +192,7 @@ scopes:
         isInfix: false
         isInline: false
         isOperator: true
-        isOverride: false
+        isOverride: true
         isStatic: false
         isSuspend: false
         modality: FINAL
@@ -485,7 +485,7 @@ scopes:
         isInfix: false
         isInline: false
         isOperator: false
-        isOverride: false
+        isOverride: true
         isStatic: false
         isSuspend: false
         modality: FINAL
@@ -513,7 +513,7 @@ scopes:
         isInfix: false
         isInline: false
         isOperator: false
-        isOverride: false
+        isOverride: true
         isStatic: false
         isSuspend: false
         modality: FINAL