Improve Create release draft workflow + templates for the free notes and...

Improve Create release draft workflow + templates for the free notes and docker images sections in the notes (#4371)

This PR has the following changes:

- New templates for the free notes and docker images sections in the
release notes. There is going to be a section for the manual additions
to the release notes + a section with the links to the docker images for
`polkadot` and `polkadot-parachain` binaries at the end of the release
draft.
- Fix for matrix section in the Create release draft flow (adds the
release environment variable)
- Reduction of the message which is posted to the announcement chats, as
the current one with the full release notes text is too big.