[Flow EVM] use big.Int for any balance related fields

[ramtinms]

closes: #5222

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (89594b2) 55.44% compared to head (42e05c5) 50.50%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5236      +/-   ##
==========================================
- Coverage   55.44%   50.50%   -4.95%     
==========================================
  Files         996      196     -800     
  Lines       95786    17433   -78353     
==========================================
- Hits        53108     8804   -44304     
+ Misses      38686     8022   -30664     
+ Partials     3992      607    -3385     

Flag	Coverage Δ
unittests	50.50% <ø> (-4.95%)	⬇️

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[turbolent]

Nice

[janezpodhostnik]

Does it make sense to have a type alias AttoFlow = *big.Int

[sideninja]

There's a panic in fvm tests.