Simplifying package release process proposal

Hello team, as Package Registry V2 is here we are in the position to enhance our package release process even more!

I started working on a [document](https://docs.google.com/document/d/1K6SH_m0MAg2PFw1ACbJlc4-h62VgiZ5-thY6cc8tW-k/edit?usp=sharing) to sketch how we could improve the package release process by building on top of what Package Registry V2 provides.

/cc @ruflin @elastic/ecosystem

Start with the linked Google document, which sketches improvements to the package release process using Package Registry V2. Confirm the intended scope, affected release entry points, and acceptance criteria with the maintainers; the issue does not identify files, tests, or a defined completion state.

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