Issue number: resolves#28180
---------
<!-- Please do not submit updates to dependencies unless it fixes an
issue. -->
<!-- Please try to limit your pull request to one type (bugfix, feature,
etc). Submit multiple pull requests if needed. -->
## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->
When presenting an overlay, we remove the root (usually
`ion-router-outlet`) from the accessibility tree. This makes it so you
cannot accidentally focus elements behind the overlay. When dismissing
an overlay we re-add the root to the accessibility tree. However, we
fail to consider if there are multiple presented overlays. For example,
if you present a modal, then an alert, then dismiss the alert, then the
root is re-added to the accessibility tree even though the modal is
still presented.
## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->
- The root is now re-added to the accessibility tree only if it is the
last presented overlay.
## Does this introduce a breaking change?
- [ ] Yes
- [x] No
<!-- If this introduces a breaking change, please describe the impact
and migration path for existing applications below. -->
## Other information
<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->
Dev build: `7.4.1-dev.11694783260.13da477f`
81714d45bd