FIR IDE: Add visibility checks to the completion

Visibility checks currently do not work in some cases, for example:

- public nested class of private class is seen globally
- private_for_this does not work
- some other cases I am not yet aware of

If `FirVisibilityChecker.isVisible` fix those issues, they will be fixed
automatically in the completion

idea/idea-completion/testData/basic/multifile/NotImportedClass/NotImportedClass.dependency.kt

@@ -0,0 +1,13 @@
+package dependency
+
+class PublicTopLevelClass {
+    class PublicNestedClass
+    protected class ProtectedNestedClass
+    private class PrivateNestedClass
+
+    inner class PublicInnerClass
+    protected inner class ProtectedInnerClass
+    private inner class PrivateInnerClass
+}
+
+private class PrivateTopLevelClass

idea/idea-completion/testData/basic/multifile/NotImportedClass/NotImportedClass.kt

@@ -0,0 +1,7 @@
+// FIR_COMPARISON
+package test
+
+fun usage(): P<caret> {}
+
+// EXIST: PublicTopLevelClass, PublicNestedClass, PublicInnerClass
+// ABSENT: PrivateNestedClass, PrivateInnerClass, ProtectedNestedClass, ProtectedInnerClass, PrivateTopLevelClass