[clangd] Make file limit for textDocument/rename configurable

[ckandeler]

Summary

Without this, clients are unable to rename often-used symbols in larger
projects.

[kadircet]

thanks!

clang-tools-extra/clangd/tool/ClangdMain.cpp

 opt<int> ReferencesLimit{
     "limit-references",
     cat(Features),
     desc("Limit the number of references returned by clangd. "
          "0 means no limit (default=1000)"),
     init(1000),
 };
 
+opt<int> RenameFileLimit{
+    "rename-file-limit",
+    cat(Features),
+    desc("Limit the number of files to be affected by symbol renaming. "
+         "0 means no limit (default=50)"),
+    init(50),
+};
+
 list<std::string> TweakList{
     "tweaks",
     cat(Features),
     desc("Specify a list of Tweaks to enable (only for clangd developers)."),
     Hidden,
     CommaSeparated,
 };
 
if (IndexFile.empty()) {
       elog("When enabling remote index, IndexFile should not be specified. "
            "Only one can be used at time. Remote index will ignored.");
     }
   }
 #endif
   Opts.BackgroundIndex = EnableBackgroundIndex;
   Opts.BackgroundIndexPriority = BackgroundIndexPriority;
   Opts.ReferencesLimit = ReferencesLimit;
+  Opts.Rename.LimitFiles = RenameFileLimit;
   auto PAI = createProjectAwareIndex(loadExternalIndex, Sync);
   if (StaticIdx) {
     IdxStack.emplace_back(std::move(StaticIdx));
     IdxStack.emplace_back(
         std::make_unique<MergedIndex>(PAI.get(), IdxStack.back().get()));
     Opts.StaticIndex = IdxStack.back().get();
   } else {
     Opts.StaticIndex = PAI.get();