net/disk_cache/sql: Add feature parameters for SQLite configuration

This CL adds two new feature parameters to kDiskCacheBackendExperiment
to allow fine-tuning the SQLite database configuration for the SQL-based
disk cache:

1. SqlDiskCacheReleaseMemoryAfterWrites: Controls whether SQLite
   aggressively releases cached memory after writes. This uses the
   release_memory_after_writes option in sql::DatabaseOptions.
2. SqlDiskCacheCacheSize: Allows overriding the SQLite cache size.

These parameters are passed to sql::DatabaseOptions in the
SqlPersistentStore::Backend constructor.

Bug: 443174708
Change-Id: Ie3ca7ce9e0434d8f0b7988bffaa8fd5c2f080b93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7604294
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1590508}
NOKEYCHECK=True
GitOrigin-RevId: f8128f49d5c6b35e03212cd4f6c8d9eeeb016d7d