disk_cache/sql: Optimize UpdateEntryLastUsed with a by-ResId variant

The existing method to update an entry's last_used timestamp required a
lookup by the entry's key (hash and string). This is inefficient when
the internal resource ID (res_id) is already known, as is the case in
SqlBackendImpl::HandleUpdateEntryLastUsedOperation.

This change introduces a new, more efficient variant,
UpdateEntryLastUsedByResId, which updates the database entry directly
using its primary key (res_id). The call site in SqlBackendImpl is
updated to take advantage of this.

The existing key-based method is renamed to UpdateEntryLastUsedByKey
for clarity.

Additionally, this change fixes a minor issue where
HandleUpdateEntryLastUsedOperation would attempt to update an entry
that had failed speculative creation. It now checks for a valid res_id
before proceeding.

Performance was measured by running the
`DiskCachePerfTest.SqlCacheBackendPerformance` test 10 times and taking
the median on an M4 Pro MacBook Pro (16-inch, Nov 2024).

|                              | ToT r1523417 | with this cl |
| -----------------------------|--------------|--------------|
| cache_entries_write_time     | 2,074.191 ms | 2,031.665 ms |
| cache_headers_read_time_cold |   850.153 ms |   836.924 ms |
| cache_headers_read_time_warm |   333.641 ms |   315.235 ms |
| cache_entries_read_time_cold | 1,204.297 ms | 1,141.335 ms |
| cache_entries_read_time_warm |   429.028 ms |   409.849 ms |

OBSOLETE_HISTOGRAMS=Replaced UpdateEntryLastUsed with UpdateEntryLastUsedByKey and UpdateEntryLastUsedByResId

Bug: 443171275
Change-Id: Ic8f0ff3700e5c45043de6a8eccfa8362b08c0157
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6998495
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Reviewed-by: Mingyu Lei <leimy@chromium.org>
Reviewed-by: Nidhi Jaju <nidhijaju@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1523433}