Rust integration

[Neopallium]

Adding Rust integration framework.

It uses a simple account "nonce" server, to allow the tests to run in parallel. This is really only needed when using Alice to onboard new identities for each test. Each test can generate new "users" (primary key onboarded and funded using Alice) for executing extrinsic calls.

[codecov[bot]]

Codecov Report

Merging #1498 (d04d904) into develop (99dc6cc) will decrease coverage by 0.01%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1498      +/-   ##
===========================================
- Coverage    53.98%   53.98%   -0.01%     
===========================================
  Files          145      145              
  Lines        32501    32501              
===========================================
- Hits         17546    17545       -1     
- Misses       14955    14956       +1     

see 4 files with indirect coverage changes