SQLite Begin Concurrent

I am also very curious if this makes any difference over just doing a mutex over a single connection and ensuring minimal contention.

The biggest TIL from this was the fact that there is a 2nd WAL mode that seems to have some additional optimizations relative to the first:

https://www.sqlite.org/cgi/src/doc/wal2/doc/wal2.md

I will definitely be experimenting with this in the future. We have some very write-heavy databases currently configured for WAL which may be able to benefit from the 2 file approach.