Bug 1658702 - part 15: Implement shortcut case of `AutoDeleteRangesHandler::HandleDeleteNonCollapsedRanges()` r=m_kato

This patch corresponds to:
* https://searchfox.org/mozilla-central/rev/0c97a6410ff018c22e65a0cbe4e5f2ca4581b22e/editor/libeditor/HTMLEditSubActionHandler.cpp#4500-4527

Depends on D90211

Differential Revision: https://phabricator.services.mozilla.com/D90212