test: print gas report, and ensure evm is killed

[pcarranzav]

• Gas report is saved to reports/ folder, but usually we want to see it in the console, so here we add a cat command to print it
• The EVM wasn't being killed properly if the tests failed, so here we add a trap to ensure the cleanup happens

[codecov]

Codecov Report

Base: 90.57% // Head: 90.57% // No change to project coverage 👍

Coverage data is based on head (0b7055a) compared to base (f1c5fe7).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #732   +/-   ##
=======================================
  Coverage   90.57%   90.57%           
=======================================
  Files          35       35           
  Lines        1762     1762           
  Branches      296      296           
=======================================
  Hits         1596     1596           
  Misses        166      166           

Flag	Coverage Δ
unittests	90.57% <ø> (ø)

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