Implement net gas metering for SSTORE in LegacyVM

[gumb0]

#5226

[gumb0]

I will better move tabs conversion to separate PR

[codecov-io]

Codecov Report

Merging #5231 into master will increase coverage by 0.17%.
The diff coverage is 97.7%.

@@            Coverage Diff             @@
##           master    #5231      +/-   ##
==========================================
+ Coverage   60.67%   60.84%   +0.17%     
==========================================
  Files         338      338              
  Lines       27450    27562     +112     
  Branches     3184     3194      +10     
==========================================
+ Hits        16656    16771     +115     
+ Misses       9667     9666       -1     
+ Partials     1127     1125       -2

[gumb0]

Code in Account/State still should be improved and better documented, but I'll add some tests first.

[gumb0]

I did some refactoring in State/Account making the caches m_storageOverlay and m_storageOriginal be updated only inside Account. This requires OverlayDB* being passed to storage getters, but still it seems simpler this way.

[chfast]

Wow. This is excellent work.