settings: Separate expand and toggle actions on toggle buttons

On the Glic settings page, the "page content sharing" row has both an
expand/collapse control and a toggle switch. Clicks on the left side of
the row, intended to expand the details, were incorrectly also
activating the toggle switch. This was because the entire
<settings-toggle-button> component was treated as a single click target.

This change introduces an boolean property to the
 component. When this property is set to true,
clicks on the row will fire a new event instead of changing the toggle's
state.

The Glic settings page is updated to use this new property and listen
for the event to correctly manage the collapsible section's visibility.
This cleanly separates the two distinct user actions and resolves the
unexpected behavior.

Demo:
https://screencast.googleplex.com/cast/NDUyNjUzNDE1NjA5MTM5MnxhMGZmOGJlMS1kZQ

Bug: 441654957
Change-Id: I07d7a0d7070113e0f023430378f4c207b87180b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6897616
Commit-Queue: Nick Birnie <birnie@google.com>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1510483}