fix(lsp): check if client is stopping before reuse #33796

Problem:
Stopping a language server and then calling vim.lsp.start() with the same name/root will return the old language server that's in the middle of shutting down. vim.lsp.start() won't return a new server until the old process has terminated.

Solution:
Introducing a client._is_stopping field that tracks the shutdown phase, preventing the client from being reused.

(cherry picked from commit 0862c1036a)

runtime/lua/vim/lsp.lua

@@ -147,7 +147,7 @@ end
 --- @param config vim.lsp.ClientConfig
 --- @return boolean
 local function reuse_client_default(client, config)
-  if client.name ~= config.name then
+  if client.name ~= config.name or client:is_stopped() then
     return false
   end