render_context_menu: Make use of ash::TryOpenUrl

Now that ash::TryOpenUrl is easily reusable, use it for the context
menu actions that open a URL (e.g. "Open link in new window").

When Lacros is enabled, the previous behavior of these actions in Ash (think: SWAs) was to always open the URL in Lacros. TryOpenUrl generally
also opens the URL in Lacros but it has a few special cases for things
like chrome:// URLs. These same special cases apply when opening the URL
by other means (e.g. shift-clicking, or even ordinary clicking for target=_blank links), so this change reduces surprises.

Bug: chromium:1444283
Change-Id: Idcd302fd7af9399487c40d137c22e1bb230f05ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4614915
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1161535}