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/TopLevelFunction/TopLevelFunction.kt

@@ -5,4 +5,5 @@ fun firstFun() {
     s<caret>
 }
 
-// EXIST: secondFun
+// EXIST: secondFun
+// ABSENT: secondFunPrivate