Add support for '--config=clang-tidy' (#3559)

This sets things up to use `bazel` to run `clang-tidy` using
https://github.com/erenon/bazel_clang_tidy.

I'm fixing issues outside of explorer, and disabling clang-tidy for
targets in explorer that have legacy issues. I was going to disable
clang-tidy for targets in explorer such as interpreter anyways, because
they're slow to parse, and just extended that to the currently failing
targets.

language_server/language_server.cpp

@@ -28,7 +28,7 @@ void LanguageServer::OnDidChangeTextDocument(
 }
 
 void LanguageServer::OnInitialize(
-    clang::clangd::NoParams const& client_capabilities,
+    clang::clangd::NoParams const& /*client_capabilities*/,
     clang::clangd::Callback<llvm::json::Object> cb) {
   llvm::json::Object capabilities{{"documentSymbolProvider", true},
                                   {"textDocumentSync", /*Full=*/1}};