feat: interative reconfigure pr

[RahulGautamSingh]

Changes

• check if reconfigure pr exists
• if reconfigure pr found, add a comment on the pr with expected pr's list and config description
• expand reconfigure cache to store extraction result so we can skip processing the reconfigure branch if it has not changed
• make slight changes mergeRenovateConfig fn such that it can pass the branchName to the detectConfigFile fn which comes in handy when trying to read the config file from reconfigure branch using api endpoint
• added tests

Context

• Closes: Interactive Reconfigure PR #547

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required (todo)

How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository 1. reconf pr Rahul-renovate-testing/recon-pr#1 (will be adding more...)

[viceice]

doesn't work on gotta and other platforms because we only have our own PRs cached

[RahulGautamSingh]

We could add this support to other platforms as per user requests.

[viceice]

it should be done in a way to not fetch all PRs

[RahulGautamSingh]

Except Gitea all other platforms has these feature implemented and in a way they fetch only that one PR.

I will try to look into how to get it done for Gitea. Would be great also to cache it in the repoCache.