Separate partitions by table in SQL-based storage backends.

[tylerwilding-wk]

Currently we store all data in a single table, eva_kv, we should partition data by table instead.

Tables, in a sense, act as partitions / groupings of data already, and have tools surrounding them for that purpose. These tools likely align with a lot of our concerns, but we cannot use them directly right now.

It's easier to consider / reuse tooling with something like a table acting as our partition (for sql at least), since the semantics for move this table from database A to database B or drop this table are much easier to get right than, say, move the set of rows matching this criteria or delete the set of rows matching this criteria from this table