Proposing a Lucene 9.12.3

Hi,

Lucene 10.3 is not yet out the door, but I’m back proposing yet another release! This time a bugfix release of 9.12.

My primary motivation for proposing this release is to resolve a number of issues related to sharing of arenas in our mmap implementation. Specifically:

 1. Reduce sharedArenaMaxPermits from 1024 to 64 (#15078)
 2. Use READONCE to read segment infos (#15074)
 3. Fix rare spin-loop in RefCountedSharedArena (#15112)

Any other potential bug fixes for 9.12.3?  I will try to find someone to be release manager or volunteer to do it myself if not. Let’s try to get an RC build out towards the end of next week, if possible.

-Chris.

P.S. I see that the following bug fix is already in branch_9_12 - Ensure vector queries handle advanceShallow correctly #14858