For #9703 - Exit fullscreen in onPause and onSessionSelected

[ekager]

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.

After merge

• Milestone: Make sure issues finished by this pull request are added to the milestone of the version currently in development.

To download an APK when reviewing a PR:

1. click on Show All Checks,
2. click Details next to "Taskcluster (pull_request)" after it appears and then finishes with a green checkmark,
3. click on the "Fenix - assemble" task, then click "Run Artifacts".
4. the APK links should be on the left side of the screen, named for each CPU architecture

[codecov-io]

Codecov Report

Merging #10016 into master will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master   #10016      +/-   ##
============================================
- Coverage     19.16%   19.16%   -0.01%     
  Complexity      521      521              
============================================
  Files           337      337              
  Lines         13762    13764       +2     
  Branches       1846     1846              
============================================
  Hits           2638     2638              
- Misses        10885    10887       +2     
  Partials        239      239              

Impacted Files	Coverage Δ	Complexity Δ
...a/org/mozilla/fenix/browser/BaseBrowserFragment.kt	0.00% <0.00%> (ø)	0.00 <0.00> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d519cf1...a580a9d. Read the comment docs.