Update files and clang-tidy config to pass with clang-tidy-20 (#4691)

Disables three new warnings because they lean more towards style
conflicts than fixes. I've brought these up on #style.

Other than that, mostly fixing basic issues, and things that
clang-tidy-20 seems to fire where clang-tiday-16 didn't. One particular
curious case is `llvm::StringLiteral::data()` uses, which are flagged as
not strictly null-terminated; I'm switching to `const char*` in those
spots which matches `llvm::formatv`'s format argument, but feels worse.

I'm removing `run_clang_tidy.py` here because I'm observing it give
fewer warnings than `bazel build --config=clang-tidy -k
//toolchain/...`. The latter matches how we enforce in GitHub actions
(and also caches results, and suppresses output for files that have no
issues), so I'm dropping the bespoke script.

toolchain/parse/extract.cpp

@@ -76,11 +76,13 @@ class NodeExtractor {
                             std::tuple<U...>* /*type*/) -> std::optional<T>;
 
   // Split out trace logic. The noinline saves a few seconds on compilation.
+  // TODO: Switch format to `llvm::StringLiteral` if
+  // `llvm::StringLiteral::c_str` is added.
   template <typename... ArgT>
-  [[clang::noinline]] auto MaybeTrace(llvm::StringLiteral format,
-                                      ArgT... args) const -> void {
+  [[clang::noinline]] auto MaybeTrace(const char* format, ArgT... args) const
+      -> void {
     if (trace_) {
-      *trace_ << llvm::formatv(format.data(), args...);
+      *trace_ << llvm::formatv(format, args...);
     }
   }