Implement EIP-1884: Repricing for trie-size-dependent opcodes in LegacyVM

[gumb0]

https://eips.ethereum.org/EIPS/eip-1884

Note that it puts repricing and SELFBALANCE behind account versioning, i.e. reduced costs and the new opcode will be active only in contracts deployed with external transaction after Istanbul fork.

If it's decided that it should be in effect for version 0, we'll need to introduce another EVMSchedule ("between" current ConstantinopleFixSchedule and IstanbulSchedule)
Account versioning is disabled in Istanbul.

[codecov-io]

Codecov Report

Merging #5700 into master will increase coverage by 0.06%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #5700      +/-   ##
==========================================
+ Coverage   63.22%   63.28%   +0.06%     
==========================================
  Files         353      353              
  Lines       30276    30322      +46     
  Branches     3390     3392       +2     
==========================================
+ Hits        19142    19190      +48     
  Misses       9898     9898              
+ Partials     1236     1234       -2

[gumb0]

cc @holiman @winsvega

[gumb0]

This is rebased and ready for review.
The current state of the EIP is "tentatively accepted".

[holiman]

LGTM

[gumb0]

Rebased.

EIP is Accepted now, please review @chfast @halfalicious

[halfalicious]

@gumb0 For reference, why was the account versioning EIP bumped from Istanbul?

[halfalicious]

How come the account version is available in the Constantinople Fix schedule..do we need to reference it in this test since from what I understand it's been punted to post-Istanbul?

[gumb0]

Versioning still exists in the code for all forks, with version being 0 in all forks before we activate version 1 (currently it's Experimental fork)

This line is actually redundant.

[halfalicious]

Should we also add the following tests from the EIP:

• balance(this) and selfbalance return the same value (first test case)
• balance(this) costs 700 gas (second test case)
• selfbalance doesn't pop from stack (third test case)

[halfalicious]

Approved with some minor questions not worth blocking merging for

[gumb0]

@halfalicious Re account versioning: for now it's decided that no changes accepted for Istanbul are radical enough to put them under versioning. Actually I'm not sure anymore it will be ever needed.