Set the Lua transform `search_dirs` option to Vector's config dir by default

As part of our recent Lua improvements we've defaulted the search_dirs option to the same directory as your Vector configuration file(s). This is usually what's expected and allows you to place all of your Vector related files together.

Upgrade Guide

Make the following changes in your vector.toml file if your Lua files are not in the same directory as your Vector configuration file:

[transform.my-script]
   type = "lua"
+  search_dirs = "/my/other/dir"

That's it!