reevaluate sqlite library

[slingamn]

See discussion on #2352:

1. Consider switching to ncruces/go-sqlite3 as the library
2. Reconsider the recommendation to set a max of 1 open connection (I've also heard of people using two separate connection pools, one for reads with multiple connections, one for writes with max 1 connection, but I've heard that this can lead to starvation of the writers, and our workload is write-heavy anyway?)

[NyaaaWhatsUpDoc]

re: 2, you don't need to do anything special to try it out. you can just up the number of max connections and it works fine as long as WAL is enabled, since the main issue with concurrent sqlite use is that doesn't support multiple concurrent processes, but multiple concurrent threads it handles fine.

which brings up another point, it would be worth updating the documentation you have mentioning use of kubernetes with a load balancer and shared volume to mention that SQLite does not support this (since you would have the potential for multiple processes accessing the same database file at once). scratch that, just seen the linked kubernetes conf only permits 1 replica :p