[Proposal] Push release tags using pipeline

[mowies]

Problem

We have lots of troubles with tags and interdependencies of them with the core and contrib repo.

Some examples:

• OCB core-repo tag being tied to the tag pushed to the releases repo (ocb release is tied to the tag being the same with the core repository release #764)
• OpAMP supervisor contrib-repo tag being tied to the tag pushed to the releases repo
• Tags not being mutable anymore per default (Deal with tags no longer being modifiable #998)

Solution

I want to propose a solution to this with a pipeline that will be manually triggered to push release tags (similar to the nightly tag pushing pipeline).
The pipeline could have various inputs for different versions that are needed for a release. I imagine something like the following things to set:

• builder tag from core repo
• opamp tag from contrib repo
• collector tag that should be pushed
• maybe
  • core tag to use
  • contrib tag to use

Some issues that this would solve I think:

• [release] Remove the need for a tag in make push-tags #879
• Deal with tags no longer being modifiable #998
• No process for doing releases with only changes from opentelemetry-collector-releases #1072

Some drawbacks:

• having the tag be pushed by a workflow means that it's not signed by a real person in the end (for better or worse 🤷🏼 )

[mx-psi]

I support doing this.

The main concern historically with this has been signing which I think we can deal with. A separate concern would be what to do if things go wrong (e.g. what happens if we end up in an intermediate state where only half the tags have been pushed). I guess we can design things in a way that allows us to complete things manually in that case