tsdb multi-backend support and testing!

[goodboy]

As per the slew of issues pertaining to time-series-db subsystems in piker seen here: https://github.com/pikers/piker/labels/tsdb

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Hi-level ToDo:

• [ ] breaking out the middle-ware history managment layer into it's own subpkg as per https://github.com/pikers/piker/issues/315
• [ ] trying out at least one other tsdb (probably arctic) and formalizing our OHLCV history apis as per the research options listed in #90
• [ ] actually documenting how to launch the db with --tsdb 😂 as per #313
• [ ] generally speaking, much better management tools for manually pulling data from providers and populating a db instance either with cli or context-menu options in our charting app!
• [ ] real-time ingest of tick and signals (from our fsp layer) as per, for eg. #314
• [ ] a tick history to 1s OHLCV downsampler system that can be used cross-provider since most don't provide this low of a sample rate (think only one is ib?)

...

maybe more?

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testing ToDo:

• [ ] db client connection, write, read and delete a time series loaded from either an offline sample or some provider we can always rely on (like kraken maybe?)
• [ ] basic tests for replication for those dbs which support it