fix(loader): cache path ambiguity #24491

Problem: cache paths are derived by replacing each reserved/filesystem-
path-sensitive char with a `%` char in the original path. With this
method, two different files at two different paths (each containing `%`
chars) can erroneously resolve to the very same cache path in certain
edge-cases.

Solution: derive cache paths by url-encoding the original (path) instead
using `vim.uri_encode()` with `"rfc2396"`. Increment `Loader.VERSION` to
denote this change.

runtime/lua/vim/loader.lua

@@ -1,4 +1,5 @@
 local uv = vim.uv
+local uri_encode = vim.uri_encode
 
 --- @type (fun(modename: string): fun()|string)[]
 local loaders = package.loaders
@@ -33,7 +34,7 @@ M.enabled = false
 ---@field _rtp_key string
 ---@field _hashes? table<string, CacheHash>
 local Loader = {
-  VERSION = 3,
+  VERSION = 4,
   ---@type table<string, table<string,ModuleInfo>>
   _indexed = {},
   ---@type table<string, string[]>
@@ -99,7 +100,7 @@ end
 ---@return string file_name
 ---@private
 function Loader.cache_file(name)
-  local ret = M.path .. '/' .. name:gsub('[/\\:]', '%%')
+  local ret = ('%s/%s'):format(M.path, uri_encode(name, 'rfc2396'))
   return ret:sub(-4) == '.lua' and (ret .. 'c') or (ret .. '.luac')
 end