Use JvmName on kotlin.Metadata parameters to improve public API

#KT-26359 Fixed

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

@@ -1,9 +1,9 @@
 <!EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata<!>
 class A
 
-<!EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(xs = "_")<!>
+<!EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(extraString = "_")<!>
 annotation class B(val m: Metadata)
 
-<!WRONG_ANNOTATION_TARGET, EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(xi = 0)<!>
+<!WRONG_ANNOTATION_TARGET, EXPLICIT_METADATA_IS_DISALLOWED!>@Metadata(extraInt = 0)<!>
 @B(Metadata())
 fun f() {}