BlockChain unit tests improvements

[gumb0]

1. New test for new method BlockChain::insertWithoutParent()

2. Make BlockChain unit tests use chain parameters with NoProof seal engine, which makes them faster and more isolated by skipping full mining

[pirapira]

Looks good to me.

[winsvega]

So now we could do a unit test with 100 blocks for ease ?

[gumb0]

@winsvega Yes, I think it should be reasonably fast

[codecov-io]

Codecov Report

Merging #4436 into develop will increase coverage by 0.09%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #4436      +/-   ##
===========================================
+ Coverage    68.29%   68.38%   +0.09%     
===========================================
  Files          305      306       +1     
  Lines        23406    23419      +13     
===========================================
+ Hits         15985    16015      +30     
+ Misses        7421     7404      -17

Impacted Files	Coverage Δ
test/unittests/libethereum/Block.cpp	95.4% <ø> (-0.06%)	⬇️
libethashseal/GenesisInfo.cpp	72% <100%> (+1.16%)	⬆️
...ethashseal/genesis/test/mainNetworkNoProofTest.cpp	100% <100%> (ø)
test/tools/libtesteth/BlockChainHelper.h	94.73% <100%> (+1.4%)	⬆️
test/unittests/libethereum/BlockChain.cpp	78.72% <100%> (+3.5%)	⬆️
test/tools/libtesteth/BlockChainHelper.cpp	77.65% <0%> (+0.57%)	⬆️
libethereum/BlockChain.cpp	70.55% <0%> (+1.16%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5eee2d4...b612e15. Read the comment docs.

[chfast]

Holy f*ck, how fast is it now? Thanks for finding this...