Diesel 2.0.0 upgrade (#2452)

* Initial commit to bump diesel to 2.0.0-rc.0 and see what happens

* Add chrono feature from diesel

* db_schema crate is close to building?

* Upgrade diesel-derive-newtype

* Mostly modifying references to connections to be mutable ones; also used
new way to do migrations as suggested by the migration guide; a lot more
compiles now, though I can't figure out this tricky ToSql issue at the
moment

* Running clippy --fix

* Trying to fix drone clippy 1

* Fix clippy

* Upgrade clux-musl

* Trying to fix drone clippy 2

* Trying to fix drone clippy 3

* Trying to fix drone clippy 5

* Adding diesel table aliases, removing sql view hack. Fixes #2101

Co-authored-by: Steven Chu <stevenc1@gmail.com>
Co-authored-by: Nutomic <me@nutomic.com>