In https://github.com/lightpanda-io/browser/pull/1774 we started to track Ranges
in the page in order to correctly make them "live". But, without correct
lifetime, they would continue to be "live" even if out of scope in JS.
This commit adds finalizers to Range via reference counting similar to Events.
It _is_ possible for a Range to outlive its page, so we can't just remove the
range from the Page's _live_range list - the page might not be valid. This
commit gives every page an unique id and the ability to try and get the page
by id from the session. By capturing the page_id at creation-time, a Range
can defensively remove itself from the page's list. If the page is already
gone, then there's no need to do anything.
Our BrowsingContext currently supports 1 target. So we have a per-BC target_id.
Previously, our target had 1 "frame" - our page. So we often treated the
targetId as the frameId. But to work with frames, we need page-specific
frameIds and loaderIds.
This tries to clean up our ids (a little). frameIds are now ids derived from
a new incrementing page.id. This page.id has to be passed around (via http
Requests and through notifications) in order to properly generate messages with
a frameId.
