[Chore] v17.3 release

[serokell-bot]

Description

This PR introduces a new release in tezos-packaging.

Follows #

Changes related to the creation of a release (conditional)

• I updated release number in meta.json.
• If the native release version was updated, I reset the letter_version in model.py.

In case the new Tezos release provides a new protocol and corresponding testnet

• I supported new protocol in protocols.json.
• I supported new protocol and testnet in native packaging.
• I supported new protocol and testnet in brew formulas.
• I added tests for the new protocol and testnet.

Things to do after this release PR is merged

Update brew bottles and repository mirrors

• I merged PR that updates bottles hashes (this PR is supposed to be created by the CI).

Update documentation

• I updated README.md.
• I updated baking doc.

[pasqu4le]

Note: this was automatically re-opened because the latest upstream tag is v17.3, which was released at the same time as v18.0-rc1, but we handled them in the opposite order.

I'm closing this but leaving the branch open, which should prevent new PRs from getting opened.