[java][switch completion] IDEA-278622 Fix completion variants in switch case label

Use the `inheritorsFilter` when the element that is being filtered is of the PsiClass type regardless if the selector class of a switch block is sealed or not. All the inheritors of the sealed class get added in JavaCompletionProcessor.

GitOrigin-RevId: 28e70b44444edad329f086a9dca0557baea03bec

java/java-tests/testData/codeInsight/completion/normal/CompleteSealedLabelSwitch.java

@@ -0,0 +1,24 @@
+
+class Main {
+  public static abstract sealed class Sealed {
+    public static final class SealedInheritor extends Sealed {}
+  }
+
+  int f(Sealed o) {
+    return switch(o) {
+      case Sealed.SealedIn<caret>, null
+    }
+  }
+
+  int g(Sealed o) {
+    return switch(o) {
+      case null, Sealed.SealedIn<caret>
+    }
+  }
+
+  int h(Sealed o) {
+    return switch(o) {
+      case Sealed.SealedIn<caret>
+    }
+  }
+}

java/java-tests/testData/codeInsight/completion/normal/CompleteSealedLabelSwitch_after.java

@@ -0,0 +1,24 @@
+
+class Main {
+  public static abstract sealed class Sealed {
+    public static final class SealedInheritor extends Sealed {}
+  }
+
+  int f(Sealed o) {
+    return switch(o) {
+        case Sealed.SealedInheritor, null
+    }
+  }
+
+  int g(Sealed o) {
+    return switch(o) {
+        case null, Sealed.SealedInheritor
+    }
+  }
+
+  int h(Sealed o) {
+    return switch(o) {
+        case Sealed.SealedInheritor
+    }
+  }
+}