Improve build workflow and release process

[remyroy]

What I did

• Merged docker workflow into the build workflow
• Added a job to create a draft release on successful build workflow
• Added steps to automatically upload built assets from the build workflow
• Added steps to automatically add the template to our release notes
• Documented the new release process
• Refactored the build-binaries job to avoid duplicating code or calls where it make sense
• Automatically generate the binaries table in the release notes
• Automatically generate the docker image table in the release notes
• Made sure the new draft release has the correct version tag when triggered by adding a tag on the repo
• Made sure that binary asset links are good after publishing the draft release

This is meant to further simplify and create a release process that is easy and less prone to errors.

Related issue

Somewhat related to #181 and the discussion we had with ToB

[remyroy]

I've streamlined the release and build process in a way to make it even easier and mostly automated.

[remyroy]

A lot of this PR is being testing on my other org/repo on https://github.com/remyroy-test/ethstaker-deposit-cli/ since you need the workflow files to be part of your main branch for them to be active and testable.

[remyroy]

This should be ready for review now.

[valefar-on-discord]

Release notes modification is very nice