feat: Add cypress test for downloading chart as image

[codemaster08240328]

SUMMARY

This pr is created to add cypress test for downloading chart as image.

Downloading chart image feature was broken several times in the past, so need to add test to confirm it.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue: fix: Chart download as image issue #19885
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #19963 (602623b) into master (6bd025d) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #19963      +/-   ##
==========================================
- Coverage   66.21%   66.20%   -0.01%     
==========================================
  Files        1715     1715              
  Lines       65061    65078      +17     
  Branches     6723     6731       +8     
==========================================
+ Hits        43079    43085       +6     
- Misses      20270    20282      +12     
+ Partials     1712     1711       -1     

Flag	Coverage Δ
javascript	51.25% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...tend/src/visualizations/FilterBox/controlPanel.jsx	0.00% <0.00%> (-37.50%)	⬇️
superset-frontend/src/views/store.ts	80.00% <0.00%> (-10.00%)	⬇️
...uperset-frontend/src/utils/getClientErrorObject.ts	63.15% <0.00%> (-8.28%)	⬇️
...nts/ExploreAdditionalActionsMenu/ExploreReport.tsx	50.00% <0.00%> (-7.90%)	⬇️
superset-frontend/src/reports/actions/reports.js	36.36% <0.00%> (-3.04%)	⬇️
...ntend/src/explore/components/ExploreChartPanel.jsx	70.49% <0.00%> (-1.18%)	⬇️
superset-frontend/src/embedded/index.tsx	0.00% <0.00%> (ø)
superset-frontend/src/types/bootstrapTypes.ts	100.00% <0.00%> (ø)
superset-frontend/src/SqlLab/reducers/sqlLab.js	33.15% <0.00%> (ø)
...rset-frontend/src/dashboard/util/findPermission.ts	92.30% <0.00%> (ø)
... and 20 more

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[rusackas]

Nice!!!