Use btm prepared statement cache (See #11033) (rebased onto dev_4_4)



This is the same as gh-1243 but rebased onto dev_4_4.

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Suggestion on the list was that the time to remove
the 1K or 10K uncached prepared statements from the
single collection was causing the long hangs. Here,
we've moved up to btm 2.1.3 and set the prepared
statement cache to 10 by default. (Note: for some
DBs this will require more active connections)