make unit test as a package

[nanne007]

As unit test has to be Std module.

[codecov]

Codecov Report

Merging #3155 (1429e6e) into master (a3e7973) will decrease coverage by 0.84%.
The diff coverage is 6.08%.

@@            Coverage Diff             @@
##           master    #3155      +/-   ##
==========================================
- Coverage   33.06%   32.22%   -0.83%     
==========================================
  Files         518      503      -15     
  Lines       46774    46233     -541     
  Branches    21278    21161     -117     
==========================================
- Hits        15461    14896     -565     
- Misses      16928    17473     +545     
+ Partials    14385    13864     -521     

Flag	Coverage Δ
unittests	32.22% <6.08%> (-0.83%)	⬇️

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

Impacted Files	Coverage Δ
block-relayer/src/block_relayer.rs	15.79% <0.00%> (ø)
config/src/lib.rs	35.12% <ø> (ø)
executor/src/account.rs	14.29% <ø> (-29.82%)	⬇️
network/api/src/messages.rs	29.38% <ø> (ø)
rpc/api/src/types.rs	14.26% <0.00%> (+0.57%)	⬆️
state/api/src/chain_state.rs	46.80% <ø> (ø)
test-helper/src/executor.rs	25.22% <ø> (ø)
types/src/lib.rs	100.00% <ø> (ø)
vm/compiler/src/bytecode_transpose.rs	0.00% <0.00%> (ø)
vm/natives/src/lib.rs	90.00% <ø> (+10.00%)	⬆️
... and 105 more

---

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 0e4eef6...1429e6e. Read the comment docs.