We previously only set the top toolbar as fixed if an a11y service was running.

We do this in order to make it easier to analyze in GLAM: see the metric
descriptions for more details.

Additionally, we change the time unit to milliseconds to make it easier
to analyze in GLAM.

This addresses the root problem we're experiencing for this issue - data
not showing up in GLAM.

This was the previous behavior for both the top and bottom toolbars.
Regressed when changing to use a new custom behavior for the top toolbar.

When entering fullscreen we will now collapse and hide the toolbar, allow the
browser to expand to the entire screen estate and then, when exiting fullscreen
expand the toolbar.
Collapsing and then expanding the toolbar will trigger the
EngineViewBrowserToolbarBehavior to place the browser below the toolbar.

 disables options menu to avoid leak
 removes on click listener to avoid leak

The test class left SearchStateKt mocked and caused other tests to fail intermittently when
running after it.

When the user opts out of telemetry, we need to reset the user identifiers
used by the experiment system, so that there's no risk of tracking the
user across the reset event if they later decide to re-enable telemetry.