Optimize bulk id-literal insert: don't insert :upserts, don't check for existence of :allocations-*

[ncalexan]

This is follow-up to #88. There, I note:

As a future optimization, :upserts do not need to be inserted; they upserted, so they already exist in the DB. (We still need to verify uniqueness and ensure no overlapping can occur.) Similarly, :allocations-* do not need to be checked for existence, so they can be written to the DB faster.

This ticket tracks implementing those optimizations, which should be a nice win when importing (or re-importing) large Places databases (see https://github.com/mozilla/tofino/issues/514).

[rnewman]

@ncalexan still valid?

[ncalexan]

@ncalexan still valid?

This one is -- I'm pretty sure I didn't special case these generations in the upsert resolution processing.