Next release of pg_hint_plan with PostgreSQL 17 compatibility

[michaelpq]

Hi all,

I have that on my tablets for some time. Let's do a new release of this module at the same time as PostgreSQL 17. I have on my TODO list a few things, as of:

1. Finish any compatibility work required for HEAD.
2. Fork a new branch called PG17, with changes on HEAD to plug in PG18.
3. Feature: plug-in query IDs rather than query string normalizations for the hint table. This has been on the table for some time, and I really want to get rid of that entirely now that query IDs are compiled in core, included for utilities.
4. Feature: Introduce a proper parser for the hint strings. bfb45447c9d4 has done most of the work to be able to extract the hints, but we still need to translate the hints to binary trees, which is something that the code now does with some manual steps in the hint type callbacks.
5. A round table of existing bugs, to see what could be addressed.
6. More work and analysis is needed for a3646e1b073c, which is still on HEAD. This has been reverted from the back-branches following plan instabilities as of bfaabf161824, and I think it's not quite safe yet in terms of parallel handling.
7. This will be the last release for PG12, with PostgreSQL 12 compatibility, following upstream that will EOL it. So let's be very careful to not break anything on this branch.

The release would be planned for September, potentially in its 2nd week but let's be flexible about that, just before PostgreSQL GA. In terms of features, I think that I'll be able to tackle item 3, not sure about 4.

If @yamatattsu , @rjuju or any others have any comments, feel free.