[clang] [clang][ASTMatcher] Add `matchesString` for `StringLiteral` which matches literals on given `RegExp` (PR #102152)

[Aaron Ballman via cfe-commits]

================
@@ -125,6 +125,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER_OVERLOAD(equals);
 
   REGISTER_REGEX_MATCHER(isExpansionInFileMatching);
+  REGISTER_REGEX_MATCHER(matchesString);
   REGISTER_REGEX_MATCHER(matchesName);
   REGISTER_REGEX_MATCHER(matchesSelector);
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AaronBallman wrote:

```suggestion
  REGISTER_REGEX_MATCHER(matchesName);
  REGISTER_REGEX_MATCHER(matchesSelector);
  REGISTER_REGEX_MATCHER(matchesString);
```
We try to keep these in alphabetical order.

https://github.com/llvm/llvm-project/pull/102152