feat(lua): add vim.func._memoize

Memoizes a function, using a custom function to hash the arguments.

Private for now until:

- There are other places in the codebase that could benefit from this
  (e.g. LSP), but might require other changes to accommodate.
- Invalidation of the cache needs to be controllable. Using weak tables
  is an acceptable invalidation policy, but it shouldn't be the only
  one.
- I don't think the story around `hash_fn` is completely thought out. We
  may be able to have a good default hash_fn by hashing each argument,
  so basically a better 'concat'.

runtime/lua/vim/treesitter/query.lua

@@ -191,12 +191,6 @@ function M.set(lang, query_name, text)
   explicit_queries[lang][query_name] = M.parse(lang, text)
 end
 
---- `false` if query files didn't exist or were empty
----@type table<string, table<string, Query|false>>
-local query_get_cache = vim.defaulttable(function()
-  return setmetatable({}, { __mode = 'v' })
-end)
-
 ---@deprecated
 function M.get_query(...)
   vim.deprecate('vim.treesitter.query.get_query()', 'vim.treesitter.query.get()', '0.10')
@@ -209,34 +203,19 @@ end
 ---@param query_name string Name of the query (e.g. "highlights")
 ---
 ---@return Query|nil Parsed query
-function M.get(lang, query_name)
+M.get = vim.func._memoize('concat-2', function(lang, query_name)
   if explicit_queries[lang][query_name] then
     return explicit_queries[lang][query_name]
   end
 
-  local cached = query_get_cache[lang][query_name]
-  if cached then
-    return cached
-  elseif cached == false then
-    return nil
-  end
-
   local query_files = M.get_files(lang, query_name)
   local query_string = read_query_files(query_files)
 
   if #query_string == 0 then
-    query_get_cache[lang][query_name] = false
     return nil
   end
 
-  local query = M.parse(lang, query_string)
-  query_get_cache[lang][query_name] = query
-  return query
-end
-
----@type table<string, table<string, Query>>
-local query_parse_cache = vim.defaulttable(function()
-  return setmetatable({}, { __mode = 'v' })
+  return M.parse(lang, query_string)
 end)
 
 ---@deprecated
@@ -262,20 +241,15 @@ end
 ---@param query string Query in s-expr syntax
 ---
 ---@return Query Parsed query
-function M.parse(lang, query)
+M.parse = vim.func._memoize('concat-2', function(lang, query)
   language.add(lang)
-  local cached = query_parse_cache[lang][query]
-  if cached then
-    return cached
-  end
 
   local self = setmetatable({}, Query)
   self.query = vim._ts_parse_query(lang, query)
   self.info = self.query:inspect()
   self.captures = self.info.captures
-  query_parse_cache[lang][query] = self
   return self
-end
+end)
 
 ---@deprecated
 function M.get_range(...)