feat: adds end timestamp to maintenance banner

[brobro10000]

Adds MAINTENANCE_ALERT_END_TIMESTAMP as a way to preset an end timestamp for the maintenance banner.

Fields have been added to internal

For all changes

• Ensure adequate tests are in place (or reviewed existing tests cover changes)
• Ensure English strings are marked for translation. See documentation for more details.

Only if submitting a visual change

• Ensure to attach screenshots
• Ensure to have UX team confirm screenshots

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes missing coverage. Please review.

Project coverage is 88.07%. Comparing base (94a1676) to head (9517655).
Report is 2 commits behind head on master.

Files	Patch %	Lines
src/components/app/data/utils.js	75.00%	2 Missing ⚠️
src/index.jsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1165      +/-   ##
==========================================
- Coverage   88.09%   88.07%   -0.03%     
==========================================
  Files         394      394              
  Lines        8360     8371      +11     
  Branches     2053     2062       +9     
==========================================
+ Hits         7365     7373       +8     
- Misses        952      955       +3     
  Partials       43       43              

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