Auto-check Release Phase for Breaking Changes

[crepererum]

What

Have a CI check or whatever that prevents maintainers from merging PR that are labeled w/ api-change Changes to the arrow API or next-major-release the PR has API changes and it waiting on the next major version while we're on a "minor release" phase.

Why

The contribution guideline say that breaking changes should only be merged according to the release schedule. As a maintainer with a reasonable busy day, I don't have a the mental capacity to manually check that for every PR.

See #7229 for example.

How

I dunno, use a CI script or something. That would obviously better if we would have a proper merge queue.

[alamb]

Maybe we can use cargo-semver-check

@logan-keede was discussing something similar in

• Add CI check for cargo-semver-checks datafusion#15408