Add UpdateSelectionBehavior to Range::UpdateSelectionIfAddedToSelection

[chromium-wpt-export-bot]

When a live range attached to a document is modified, this change is
upstreamed to the FrameSelection. New spec [1] says to only update
the composed live range (frame selection)'s start position if setStart
is called and only update end position if setEnd is called:
whatwg/dom#1342

This is the proposal (B) discussed here:
whatwg/dom#772 (comment)

To do this, we define enum UpdateSelectionIfAddedToSelection to have
three possible update selection behavior:

1. kAll, set selection to have the same start and end as range.
   --> Default case, when both setStart, setEnd are called.
2. kStartOnly, set selection to have the same start as range only.
   --> When only setStart is called.
3. kEndOnly, set selection to have the same end as range only.
   --> When only setEnd is called.

We add a WPT test for this new behavior, which only affects the output
of getComposedRanges() as it is the only API that accesses the frame
selection's endpoints directly.

Change-Id: I51ea53fe6156164ba3fbe38b14bc47ff502633b1
Bug: 40286116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6188157
Reviewed-by: Siye Liu <siliu@microsoft.com>
Commit-Queue: Di Zhang <dizhangg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1411209}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.