For #19820: Add labels for month and year spinners.

[mcarare]

Fixes #19820

This follows the guidelines described in
developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/listbox_role

Note: As spinners do not have a label or a hint property, the only viable solution that follows UX design is to provide labels that are not visible (have 0 height and 0 width)

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not:
  No relevant unit tests for Talkback announcements.
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
  No visual changes.
• 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.

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-commenter]

Codecov Report

Merging #19870 (3e09195) into master (103598d) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master   #19870      +/-   ##
============================================
- Coverage     36.69%   36.67%   -0.02%     
  Complexity     1606     1606              
============================================
  Files           534      534              
  Lines         20823    20868      +45     
  Branches       3098     3103       +5     
============================================
+ Hits           7640     7654      +14     
- Misses        12307    12333      +26     
- Partials        876      881       +5     

Impacted Files	Coverage Δ
...java/org/mozilla/fenix/perf/PerformanceInflater.kt	80.00% <0.00%> (-15.00%)	⬇️
...a/org/mozilla/gecko/search/SearchWidgetProvider.kt	30.95% <0.00%> (-4.95%)	⬇️
...in/java/org/mozilla/fenix/perf/NavGraphProvider.kt	62.50% <0.00%> (ø)
...c/main/java/org/mozilla/fenix/home/HomeFragment.kt	3.42% <0.00%> (+1.00%)	⬆️

---

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 103598d...3e09195. Read the comment docs.