[gitresolver] Switch from git-go git-clone to use providers API

[chmouel]

Feature request

On large (mono)?repository, a git clone may take times a lot of time, if we need to just checkin a few files.

It would be nice if we could instead use Git providers (i.e: github/gitlab) APIs instead of checking out the full tree just to grab a few files.

We may along the way will be able to support private repository in gitresolver.

Use case

Large repository checking,

Note

• We can just use go-scm to abstract a lot of the naughty different api implementation but the devil may be in the details of each provider.
• User may be able to provider access "token" for auth and ratelimit.
• We can still use anonymous for at least github and maybe other git providers.

[abayer]

In practice, we'll probably want to keep the git resolver for cases where the user is using a repo that isn't on a supported provider, but it does feel like it'll make sense to add github, gitlab, etc resolvers to explicitly support credentials, API-driven fetching of individual files, etc.

[tekton-robot]

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