feat: Implement branch matching in repo-level config

[0x416e746f6e]

This PR adds the possibility to match branches in repo-level atlantis.yaml config file.

With this it becomes possible to use atlantis to deploy different projects for different base branches of the PR (for example: the PR towards develop branch would deploy dev environment, while the PR towards main would go into production).

[0x416e746f6e]

f.w.i.w., this is a re-incarnation of #1833 (I simply did not have time when eventually @jamengual responded).

hopefully, this time we will be able to merge it.

[jamengual]

we will review as soon as we can @0x416e746f6e we are all really busy people sadly.

[0x416e746f6e]

Why "sadly"? Being very busy probably means being full-time employed => which is as very good thing for IT folks nowadays. :)

[jamengual]

touche

[jamengual]

@0x416e746f6e could you fix the conlficts?

[0x416e746f6e]

This was done @jamengual

[jamengual]

@0x416e746f6e Thanks for the contribution