Add a Reset method on CoverageReport type

[m-Peter]

Closes #2385

Description

Add a Reset method on CoverageReport type. This is helpful when CoverageReport is used in a context such as the Flow emulator, and the user/developer wants to flush everything. The ExcludedLocations, however, still remain intact.

Ref: onflow/flow-emulator#332 (comment)

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov]

Codecov Report

Merging #2386 (9736b17) into master (e9451ba) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 9736b17 differs from pull request most recent head 2ede447. Consider uploading reports for the commit 2ede447 to get more accurate results

@@            Coverage Diff             @@
##           master    #2386      +/-   ##
==========================================
- Coverage   78.52%   78.52%   -0.01%     
==========================================
  Files         316      316              
  Lines       68554    68549       -5     
==========================================
- Hits        53830    53825       -5     
  Misses      12925    12925              
  Partials     1799     1799              

Flag	Coverage Δ
unittests	78.52% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
runtime/coverage.go	100.00% <100.00%> (ø)

... and 8 files with indirect coverage changes

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[turbolent]

Good idea!