host: Make EOF opaque for EXTCODE* instructions

[axic]

[axic]

@chfast @gumb0 any feedback on the direction (before I start adding tests / more code)?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.05%. Comparing base (05ee922) to head (b67c8bb).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #587   +/-   ##
=======================================
  Coverage   98.05%   98.05%           
=======================================
  Files         116      117    +1     
  Lines       11455    11487   +32     
=======================================
+ Hits        11232    11264   +32     
  Misses        223      223           

Flag	Coverage Δ
blockchaintests	59.75% <ø> (ø)
statetests	62.14% <100.00%> (+0.02%)	:arrow_up:
statetests-silkpre	24.02% <16.12%> (-0.05%)	:arrow_down:
unittests	96.51% <100.00%> (+0.12%)	:arrow_up:

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

Files	Coverage Δ
test/state/host.cpp	95.95% <100.00%> (+0.03%)	:arrow_up:
test/unittests/state_transition_extcode_test.cpp	100.00% <100.00%> (ø)

[pdobacz]

Uses tests from https://github.com/ethereum/tests/pull/1353, which contains some changes on top of the currently used tag for testing EOF in CI state-tests.