Add race-network-and-cache source to SW router rule mojo and database class.

This CL adds a new race-network-and-cache source to ServiceWorker router
rule mojo and to service worker database class for read/write.

This CL also changes ServiceWorkerRouterSource design by removing
ServiceWorkerRouterRaceSourceEnum and rename RaceSource to
RaceNetworkAndFetchEventSource and SW DB proto accordingly to avoid
confusion with the RaceSource enum.

To support race-network-and-cache source in
https://github.com/WICG/service-worker-static-routing-api/blob/main/final-form.md#race-network-and-cache-storage

Future CLs include changes to ServiceWorker evaluator, resource loaders,
IDL and DevTools.

Bug: 370844790
Change-Id: I13269bcfe6a453fe6dbb89df10b814ee5ef1a125
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6374322
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Liang Zhao <lzhao@microsoft.com>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Commit-Queue: Monica Chintala <monicach@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1444967}