[FMV][AArch64] Convert user facing priority syntax to internal.

This allows the user to specify "priority=[1-32];featA+featB"
where priority=1 means highest priority. If the explicit
priority string is omitted then the priority of "featA+featB"
is implied, which is lower than priority=32.

Depends on llvm#146092.

Author: labrinea

clang/include/clang/Sema/Sema.h

@@ -4911,7 +4911,8 @@ class Sema final : public SemaBase {
   bool checkTargetAttr(SourceLocation LiteralLoc, StringRef Str);
 
   /// Check Target Version attrs
-  bool checkTargetVersionAttr(SourceLocation Loc, Decl *D, StringRef Str);
+  bool checkTargetVersionAttr(SourceLocation Loc, Decl *D, StringRef Str,
+                              SmallString<64> &);
   bool checkTargetClonesAttrString(
       SourceLocation LiteralLoc, StringRef Str, const StringLiteral *Literal,
       Decl *D, bool &HasDefault, bool &HasCommas, bool &HasNotDefault,