Replace v8 with monocart for coverage

[HarelM]

Launch Checklist

In order to solve the coverage issues introduced with v8 and the render test a different coverage tool is needed apparently.
See here:
cenfun/monocart-coverage-reports#4
And here:
istanbuljs/v8-to-istanbul#238

• Confirm your changes do not include backports from Mapbox projects (unless with compliant license) - if you are not sure about this, please ask!
• Briefly describe the changes in this PR.
• Link to related issues.
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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7decb26) 85.92% compared to head (b380686) 83.31%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3598      +/-   ##
==========================================
- Coverage   85.92%   83.31%   -2.61%     
==========================================
  Files         244      244              
  Lines       48269    32200   -16069     
  Branches     5152     4398     -754     
==========================================
- Hits        41473    26828   -14645     
+ Misses       6796     5124    -1672     
- Partials        0      248     +248     

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[HarelM]

Thanks @neodescis! I'm still looking for a complete solution. While this fix is in the right direction, it still doesn't fix the entire problem as there are reported "missing" end brakets.
I have an idea how to solve this, but it might not work and I'll simply merge this fix.

[HarelM]

It's better than what we currently have, I'll merge this and see how to continue improving this in the future.