[ci] Add a sandbox optional step for flaky e2e tests (#7378)

[aHenryJard]

Proposed changes

Because flaky end to end test run fine locally most of time, we need a way to run them without annoying everyone.

• Add a drone step to run flacky e2e test without failing build.
• Run after the "normal" end to end step to avoid having flake on tests because of the sandbox one.

Related issues

• Relates to #7378 work, does not close it.

Checklist

• [ ] I consider the submitted work as finished
• [ ] I tested the code for its functionality
• [ ] I wrote test cases for the relevant uses case (coverage and e2e)
• [ ] I added/update the relevant documentation (either on github or on notion)
• [ ] Where necessary I refactored code to improve the overall quality

Further comments

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 66.11%. Comparing base (199701a) to head (faa6882). Report is 116 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8167      +/-   ##
==========================================
+ Coverage   66.03%   66.11%   +0.08%     
==========================================
  Files         597      597              
  Lines       59701    59855     +154     
  Branches     6075     6127      +52     
==========================================
+ Hits        39425    39576     +151     
- Misses      20276    20279       +3     

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[aHenryJard]

I'm not sure that it's really needed, and I don't want to complexify the drone build if not necessary, keeping that work as draft for now.