NOSNOW: Revert Spark4 work for the upcoming 3.1.9 release

[sfc-gh-helmeleegy]

Spark 4 work is planned to be restored for a followup (BCR) release (after 3.1.9).

[sfc-gh-bli]

LGTM

[codealchemy]

Process question from an observer here: could the relevant commits be cherry-picked to a (stable) version branch instead of reverts (and reverts of reverts) on `master?

(perhaps a documented release process would be helpful, otherwise I just noticed the spark_<version> branches here and though it might be helpful for myself/others to ask).

[sfc-gh-helmeleegy]

Process question from an observer here: could the relevant commits be cherry-picked to a (stable) version branch instead of reverts (and reverts of reverts) on `master?

(perhaps a documented release process would be helpful, otherwise I just noticed the spark_<version> branches here and though it might be helpful for myself/others to ask).

Thanks for your question, and for the documentation note! We're adopting a cross-build model, but before our next major release, we wanted to have one more 3.1.x patch. Then we plan to ship cross-build + Spark 4 + JDBC 4 together. The revert/restore operations are meant to keep master as the source of truth.