cache sqltable query

[SimonCropp]

• cache sql QueueLengthQuery on table to avoid calculating it every time in the fast path
• use _fullTableName in calculation of query and re-use it in quals, hashcode, and tostring
• remove SqlNameHelper.Unquote since not used
• enabled nullable checks for SqlNameHelper and SqlTable

[DavidBoike]

This looks like a good change but we decided we didn't have time to fully kick the tires and still release 5.5 today. Should be considered for the next release.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[SimonCropp]

@DavidBoike can u re open and disable that stale PR bot. clearly the Particular process moves slower than that bot closes PRs

[DavidBoike]

Your comment alone would have resulted in the stale label being removed within 24 hours, but thanks for the reminder, I looked at this and I'm going to get it shipped in 5.7.0 next week.