[No-Vary-Search] Add no-vary-search to parsed_headers

Populate no-vary-search header information in parsed_headers.
Add tests for no-vary-search parsed_headers with and without the
PrefetchNoVarySearch feature enabled.

Bug: 1378075, 1378072
Change-Id: I3061a210aa309c2ea1bab497d87f97bc66597303
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4006836


Commit-Queue: Liviu Tinta <liviutinta@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Max Curran <curranmax@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1072419}