[clang-tools-extra] [clang-tidy] Extend `performance-faster-string-find` to handle ternary operator arguments (PR #187069)

[Victor Chernyakin via cfe-commits]

================
@@ -55,8 +61,7 @@ void FasterStringFindCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
 }
 
 void FasterStringFindCheck::registerMatchers(MatchFinder *Finder) {
-  const auto SingleChar =
-      ignoringParenCasts(stringLiteral(hasSize(1)).bind("literal"));
+  const auto SingleChar = expr().bind("literal");
----------------
localspook wrote:

I don't really like that we would be introducing repetition into the code

I could stick this part:
```cpp
  if (!utils::forAllLeavesOfTernaryTree(Literal, [](const Expr *E) {
        const auto *Literal = dyn_cast<StringLiteral>(E);
        return Literal && Literal->getLength() == 1;
      }))
    return;
```
into a custom matcher though

https://github.com/llvm/llvm-project/pull/187069