test: Export withdrawals to JSON state tests

[chfast]

No description provided.

[chfast]

I implemented exporting "withdrawals" to JSON to fix round-trip JSON testing, but the test still don't pass.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 29.76%. Comparing base (35b7475) to head (5ab9886).
Report is 84 commits behind head on master.

Files with missing lines	Patch %	Lines
test/unittests/state_transition.cpp	0.00%	8 Missing ⚠️
test/unittests/state_transition_block_test.cpp	0.00%	2 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (35b7475) and HEAD (5ab9886). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (35b7475)	HEAD (5ab9886)
unittests	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1000       +/-   ##
===========================================
- Coverage   93.84%   29.76%   -64.09%     
===========================================
  Files         146      146               
  Lines       15460    15468        +8     
===========================================
- Hits        14509     4604     -9905     
- Misses        951    10864     +9913     

Flag	Coverage Δ
eof_execution_spec_tests	17.41% <0.00%> (-0.01%)	⬇️
ethereum_tests	27.79% <0.00%> (-0.02%)	⬇️
ethereum_tests_silkpre	19.47% <0.00%> (-0.02%)	⬇️
execution_spec_tests	18.92% <0.00%> (-0.01%)	⬇️
unittests	?

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

Files with missing lines	Coverage Δ
test/unittests/state_transition_block_test.cpp	0.00% <0.00%> (-100.00%)	⬇️
test/unittests/state_transition.cpp	0.00% <0.00%> (-97.59%)	⬇️

... and 103 files with indirect coverage changes