RTC: Transients for awareness and JIT meta cache flushing

[peterwilsoncc]

This does a few things:

• Moves awareness to the transients API: For sites with a persistent cache awareness will be stored in the object cache, the options table for site that don't
• As the transients have a timeout set, they will not be autoloaded or invalidate the alloptions cache
• Reduces awareness granularity to 10 seconds (rounded up), this changes the awareness timeout to be anywhere between 30 and 39 seconds which is close enough. It will also reduce database writes/cache invalidation
• Introduces a filter wp_sync_awareness_timestamp_granularity to allow granularity to be modified by third party devs
• Reverts r62099 to use the Meta APIs for syncing updates: I think this will be helpful as rooms meta data will no longer be updated following an awareness update. This will allow the cache to be used for rooms that have not had an update since the last polling update (eg, browser open while making lunch)
• Introduces just in time cache invalidation for meta queries in WP_Query -- modifying the meta data will set a flag that the WP_Query post group will need to be invalidated next time a site makes a meta query
• Adds tests for above

Trac ticket: https://core.trac.wordpress.org/ticket/64696

Use of AI Tools

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[github-actions]

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[peterwilsoncc]

Kind of tempted to just set this for a day given the patterns room is shared for all posts.