feat: Disable wal_autocheckpoint

From https://www.sqlite.org/wal.html:
> The default strategy is to allow successive write transactions to grow the WAL until the WAL
  becomes about 1000 pages in size, then to run a checkpoint operation for each subsequent COMMIT
  until the WAL is reset to be smaller than 1000 pages. By default, the checkpoint will be run
  automatically by the same thread that does the COMMIT that pushes the WAL over its size
  limit. This has the effect of causing most COMMIT operations to be very fast but an occasional
  COMMIT (those that trigger a checkpoint) to be much slower.

And while autocheckpoint runs in the `PASSIVE` mode and thus doesn't block concurrent readers and
writers, in our design it blocks writers because it's done under `write_mutex` locked and thus may
cause the app to stuck for noticeable time. Let's disable autocheckpointing then, we can't rely on
it anyway.

Author: iequidoo

src/sql.rs

@@ -729,6 +729,7 @@ fn new_connection(path: &Path, passphrase: &str) -> Result<Connection> {
          PRAGMA busy_timeout = 0; -- fail immediately
          PRAGMA soft_heap_limit = 8388608; -- 8 MiB limit, same as set in Android SQLiteDatabase.
          PRAGMA foreign_keys=on;
+         PRAGMA wal_autocheckpoint=N;
          ",
     )?;