Enable WAL mode on WebDatabase

Adding the WebDatabase to the SQLWALmode Experiment.

The WAL mode is a journaling mode that is less intense on flushes
and provides performance improvements on IO contention and power.

bug: 40549957
Change-Id: Ib9515545178f18b59a20c091375eeef377dad5dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5597102


Reviewed-by: Dominic Battré <battre@chromium.org>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1312942}