UPDATE with VALUES optimization for Postgres. Various macro refactoring.

[deusaquilus]

Fixes: UPDATE values issue (TODO find number)
Also fixes: #2563

Implement equivalent of INSERT-VALUES optimization #2565 for UPDATE queries. Only Postgres supported for now but potentially other DBs in future. Also enabling mixes lifts.

• Additional config called IdiomContext which wraps TranspileConfig as well as other meta-info needed during idiom functions e.g. the ident of the batch query. Potentially other info in the future.
• Action macro changes and ReifyStatement changes needed to accomodate additional use-cases for lifting.
• The translateBatch verb still uses old Batch Mechanism TODO to update that to the new function.