More changes in templates

[jesmrec]

Changes in the templates:

• In pull request template:

  • Add release notes in advance to give time to be translated. Removed from issue template.

• In release template:

  • Move the signing tag to the end of the checklist, to assure there are no commits between the approved and the merge
  • Clarify that release branches will not be rebased anymore (direct merge instead)
  • New patch release section, with tasks for minor bugfixes

Please @JuancaG05 and @Aitorbp review this and throw as many questions as needed to understand correctly the complete processes and why changes are suggested. Specially, the tasks in patch releases.

[jesmrec]

I will add additionally two steps to the OEM release template. In case a branch is needed for such release, it has to be merged as well