tests: discover state/blockchaintests by individual test

[pdobacz]

Tackles the point (3.) from github.com/ethereum/execution-spec-tests/pull/2243 (consume direct using evmone in EEST).

Here we switch statetest and blockchaintest runners to discover gtests by parsing the JSON files and recognizing each test.

The downside is that the invocation we use in CI (just ...evmone-statetest ... fixtures/state_tests) became very chatty, so --gtest_brief=1 was added. There is an option to only go inside the JSONs when a single .json file path is given (as consume direct does), but this would complicate things quite a bit, requiring us to have more code, but not terribly much more.

Makes consume direct for evmone version in PR mentioned 👇 work correctly

[codecov]

Codecov Report

❌ Patch coverage is 92.06349% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.09%. Comparing base (0591d81) to head (70f14a6).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
test/blockchaintest/blockchaintest.cpp	87.87%	2 Missing and 2 partials ⚠️
test/statetest/statetest.cpp	96.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1331      +/-   ##
==========================================
+ Coverage   87.07%   87.09%   +0.02%     
==========================================
  Files         169      169              
  Lines       24820    24864      +44     
  Branches     4076     4081       +5     
==========================================
+ Hits        21611    21656      +45     
+ Misses        548      546       -2     
- Partials     2661     2662       +1     

Flag	Coverage Δ
eest-develop	84.17% <ø> (ø)
eest-develop-gmp	15.83% <19.04%> (-0.02%)	⬇️
eest-legacy	11.10% <15.87%> (-0.01%)	⬇️
eest-legacy-silkpre	17.56% <20.63%> (-0.02%)	⬇️
evmone-unittests	83.89% <77.77%> (+0.19%)	⬆️

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

Components	Coverage Δ
core	93.55% <ø> (ø)
tooling	86.50% <92.06%> (+0.36%)	⬆️
tests	84.13% <ø> (ø)

Files with missing lines	Coverage Δ
test/statetest/statetest.cpp	92.85% <96.66%> (-2.02%)	⬇️
test/blockchaintest/blockchaintest.cpp	87.05% <87.87%> (+8.37%)	⬆️

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[pdobacz]

It seems that discovering tests individually has more problems than I thought initially, if you apply it always. Problems which arise:

1. When calling with a dir with many tests it becomes quite unresponsive, as it discovers the tests for a long time before giving any output
2. It becomes problematic to filter out tests

Would it work for us if discover was done as it used to be (per file) when provided with a dir path (e.g. like we do in our CI) and discover per test when provided with a single .json file path (e.g. like what consume direct uses)? @chfast

EDIT: We seem to have decided it would work, this PR takes this approach