Prohibit explicit usage of kotlin.Metadata as annotation

compiler/testData/diagnostics/testsWithStdLib/annotations/explicitMetadata.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -INVISIBLE_MEMBER -INVISIBLE_REFERENCE -EXPOSED_PARAMETER_TYPE
+
+<!EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata<!>
+class A
+
+<!EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(xs = "_")<!>
+annotation class B(val m: Metadata)
+
+<!WRONG_ANNOTATION_TARGET, EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(xi = 0)<!>
+@B(Metadata())
+fun f() {}