Remove CacheInvalidateRelcacheByTuple and put CronJobCacheValid in shmem

[fanfuxiaoran]

There is no need to call CacheInvalidateRelcacheByTuple when only updating the content of cron.job table( CacheInvalidateRelcacheByTuple should be called when the schema of crom.job udpated). Each time the CacheInvalidateRelcacheByTuple is called, the Relaion of pg_cron in launcher will be rebuilt which can lead some overhead.

Instead, put CronJobCacheValid into shmem, and set it to false in function InvalidateJobCache.

[fanfuxiaoran]

@microsoft-github-policy-service agree [company="{your company}"]

[fanfuxiaoran]

@microsoft-github-policy-service agree

[marcoslot]

Closing this, since the current design seems to introduce bugs without solving a problem.