Refactor GetFreshnessLifetimes to Extract Cache-Control Once

Refactored the HttpResponseHeaders::GetFreshnessLifetimes method to
improve efficiency by extracting and parsing the Cache-Control header
values only once. This change eliminates the need to loop for
Cache-Control header in the header list, reducing redundant operations
and enhancing overall performance.

Bug: 399272772
Change-Id: I8d330ffa6d8787b3e83f43d033666fd836de7752
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6310135
Commit-Queue: Mayur Patil <patilmayur@microsoft.com>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1429526}