History Embeddings: Create SQL Delete methods used for clearing History

Adding SQL delete methods that are going to be used for clearing
storage in sync with History deletions (either manual or by expiry).

These still aren't hooked up yet, but that will be a followup.

There are unit tests to test this SQL functionality.

Bug: 329495955
Change-Id: Ie3cc81d431c169792b5a800d4dc0d76bc20703fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5368625


Commit-Queue: Tommy Li <tommycli@chromium.org>
Reviewed-by: Orin Jaworski <orinj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1277215}