FIR: rename HIDDEN to INVISIBLE_REFERENCE

Some of them should be INVISIBLE_MEMBER though

compiler/testData/diagnostics/tests/classObjects/ClassObjectVisibility.fir.kt

@@ -2,7 +2,7 @@ package foo
 
 fun test() {
   A.d
-  A.Companion.<!HIDDEN!>f<!>
+  A.Companion.<!INVISIBLE_REFERENCE!>f<!>
   B.D
   CCC
   CCC.classObjectVar

compiler/testData/diagnostics/tests/classObjects/invisibleClassObjects.fir.kt

@@ -35,14 +35,14 @@ import a.D
 
 fun test() {
     f(A)
-    f(<!HIDDEN!>B<!>)
+    f(<!INVISIBLE_REFERENCE!>B<!>)
     f(C)
-    f(<!HIDDEN!>D<!>)
+    f(<!INVISIBLE_REFERENCE!>D<!>)
 
     A.foo()
-    <!HIDDEN!>B<!>.bar()
+    <!INVISIBLE_REFERENCE!>B<!>.bar()
     C.baz()
-    <!HIDDEN!>D<!>.quux()
+    <!INVISIBLE_REFERENCE!>D<!>.quux()
 
     a.A.foo()
     a.C.baz()