* use direct blocking calls for SQLite in `sqlx_macros`
* this also ensures the database is closed properly, cleaning up tempfiles
* don't send `PRAGMA journal_mode` unless set
* this previously defaulted to WAL mode which is a permanent setting
on databases which doesn't necessarily apply to all use-cases
* changing into or out of WAL mode acquires an exclusive lock on the database
that can't be waited on by `sqlite3_busy_timeout()`
* for consistency, `sqlx-cli` commands that create databases will still
create SQLite databases in WAL mode; added a flag to disable this.
* in general, don't send `PRAGMA`s unless different than default
* we were sending a bunch of `PRAGMA`s with their default values just to enforce
an execution order on them, but we can also do this by inserting empty slots
for their keys into the `IndexMap`
* add error code to `SqliteError` printout
* document why `u64` is not supported
- adds a -r flag whihc will create a reversible migration
- add revert subcommand, which reverts the last migration
- add --dry-run flag to migration run command, which list the migrations that will be applied
- updates add migration to check if all migration are of same type, i.e cannot mix and match reversible and simple migrations
