Support `runs-on/cache` (https://github.com/runs-on/cache)

not sure if the setup-gradle action is using action/cache but i guess not. would using https://github.com/runs-on/cache still work to move away from the github cache storage. if not consider this a request to support other storage backend 🙇

thanks for the great work

Start by inspecting how the setup-gradle action currently uses caching, then compare its behavior with runs-on/cache. Determine whether that backend can replace GitHub cache storage or what support for another storage backend would require; done means the compatibility question is answered with an implementation or a clear documented limitation.

Written by the indexing model from the issue text.