Updating the docs tooling around the release process
The main change is that we will now use the `cargo release --no-publish`
flag to avoid publishing to `crates.io` until the release PR is approved.
Added the `--execute` flag by default. I don't think we need to do dry
runs since we're now only creating a commit and waiting for PR approval.
Updated `release-process.md` to reflect the new process.
I left the current wording about separating `uniffi` releases from the
rest of the crates, although I noticed that in practice we haven't been
doing that. All of our major changes in the last year bumped
`UNIFFI_CONTRACT_VERSION`, so we never had a chance to, for example,
bump the `unffi-bindgen` version without also bumping the `uniffi`
version. Maybe we should revisit this decision, but I didn't want to do
that in this change.
A consequence of the last note is that we still need to make the 2
`Chore: Release` commits.
