Add a cache for version resolution

[zxiiro]

The pin command currently calls the GitHub API for every case of uses: it finds without consideration of if it's already received a result. To make this more efficient and not eat up our ratelimit we should add a cache such that for every version lookup that happens eg actions/checkout@v4 that it resolves it should cache the result so that if the same action version is found again later in the file or across other files it can skip the API call entirely and used the cached response.

[netomi]

Accessing the GH API is done using conditional requests with a caching backend.

So normally that should be good enough, adding an additional cache would complicate things without any gain imho.

[netomi]

but we should test if the cache backend works as expected tbh.