Consider rewriting the autobumper in golang

[mudler]

Is your feature request related to a problem? Please describe.
The autobumper which is responsible of @cOS-cibot automated PRs is currently implemented in bash and using yq (https://github.com/Luet-lab/extensions/blob/master/extensions/autobump-github/luet-autobump-github). Although it works, it reached it's implementation limits and the lack of tests makes hard to implement new features

Describe the solution you'd like

A reimplementation of the auto-bumper, for e.g. in golang, complete of test-suite.

During #602 (comment) for example we could have introduced the ability to handle different package versions in the same tree, as the bash version now just does handle bumps by editing the specfiles in place.

A WIP comprensive of unit tests is here: https://github.com/mudler/luet-autobumper, it is not feature-parity yet with the bash equivalent but it already auto-bumps inplace or either add new spec files to the tree. It also handles reverse dependencies correctly.

Describe alternatives you've considered
Currently with #653 we address to #602 by allowing all the released-ever metadata to be installed. We download the available metadata in the repository before publishing the new tree version.

Additional context
See #602 and #653