[Backport 2.x] Backporting #1409 Panels Tests Updates

[sejli]

Description

• Manual backport for [MAINTENANCE] Improving Jest Test Coverage for Observability Dashboards and Fixing Cypress Tests  #1409, cherry picking 1211e83.
• Commit message on 0402b04 is a typo, should be 1211e83.
• Test for fetchAggregatedBins() was removed since it doesn't exist in 2.x.

Issues Resolved

#201 #1278

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (3afae5c) 55.01% compared to head (0402b04) 56.85%.

Files	Patch %	Lines
...lic/components/custom_panels/custom_panel_view.tsx	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              2.x    #1441      +/-   ##
==========================================
+ Coverage   55.01%   56.85%   +1.83%     
==========================================
  Files         315      318       +3     
  Lines       11182    11524     +342     
  Branches     2933     3005      +72     
==========================================
+ Hits         6152     6552     +400     
+ Misses       4980     4920      -60     
- Partials       50       52       +2     

Flag	Coverage Δ
dashboards-observability	56.85% <33.33%> (+1.83%)	⬆️

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