Add ViewUrlIgnoreCache to bypass stale cache results.

This CL adds ViewUrlIgnoreCache to the DomDistillerService interface.
This method ensures that a distillation request triggers a fresh
distillation of the current page content, bypassing any stale results
previously stored in the DistilledContentStore.

This fixes a bug in desktop reading mode where pages that update their
content (e.g., hiding/showing elements via CSS) without changing their
URL would show stale results because the service would return the cached
version based on the identical URL.

A unit test is added to verify that the cache is correctly bypassed when
stale content is present in the store and this function is used.

Bug: 483084846
Change-Id: I78bb248ac64807f36c882362ca222de4816d5127
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7576973
Reviewed-by: Brandon Wylie <wylieb@google.com>
Reviewed-by: Eitan Goldberger <eitang@google.com>
Commit-Queue: Gustavo Martin <gusmartin@google.com>
Cr-Commit-Position: refs/heads/main@{#1586587}