Browser.EXTRA_APPLICATION_ID/EXTRA_CREATE_NEW_TAB support

[buttercookie42]

Apps wanting to open an URL in the browser can pass along a Browser.EXTRA_APPLICATION_ID Intent extra, meaning they'd like to re-use an already existing tab with the same ID if it already exists instead of opening a new tab.

They can also override that behaviour by also passing along Browser.EXTRA_CREATE_NEW_TAB, which means they'd like to use a fresh tab regardless of whether another tab matching the EXTRA_APPLICATION_ID supplied already exists or not.

┆Issue is synchronized with this Jira Task

[buttercookie42]

One additional thing not to forget from the Fennec implementation:
Whenever the user opens some other URL in a tab through the browser UI, we clear any possibly stored EXTRA_APPLICATION_ID for that tab, so it can no longer be re-used (thereby overwriting the user's new URL) if another Intent containing an EXTRA_APPLICATION_ID arrives.
What's debatable (and I don't think Fennec does this right now) is whether the same thing might be worth doing if the user navigates by doing something inside the GeckoView, i.e. clicking a link or whatever we can detect as a user-triggered navigation.

[buttercookie42]

Requested in https://bugzilla.mozilla.org/show_bug.cgi?id=1620957.

[csadilek]

Moved to bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1809994

Change performed by the Move to Bugzilla add-on.