Address code review comments.

TransactionMap::sizeAsLong() optimized - temp map eliminated

1177 recover leak

Improve concurrency of connection pool with wait-free implement

Improve naming of the object id field in Prepared

Do not change ID of existing constraints in AlterTableAddConstraint

Drop TransactionMap.readLogId

Improve CURRENT_TIMESTAMP and add LOCALTIME and LOCALTIMESTAMP

Improve precision of CURRENT_TIMESTAMP on Java 9+ and change its return type to required by standard

Magic value replacement with constant

Introduce last commited value into a VersionedValue

tighten test conditions - do not ignore any exceptions

change synchronize to Atomic for untilAnalyzeCounter

Remove mapid

assorted minor refactorings

remove maps registry from TransactionStore, because it duplicates MVStore's one

protect first background exception encountered and relate it to clients

Yet another attempt to tighten that testing loop