NI-PoRep support

[rvagg]

#1999 rebased on master with some minor changes and local Cargo.toml linking

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 3.57143% with 27 lines in your changes missing coverage. Please review.

Project coverage is 75.63%. Comparing base (206a772) to head (d778998).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2010      +/-   ##
==========================================
- Coverage   75.67%   75.63%   -0.04%     
==========================================
  Files         155      155              
  Lines       15669    15676       +7     
==========================================
  Hits        11857    11857              
- Misses       3812     3819       +7     

Files	Coverage Δ
shared/src/sector/registered_proof.rs	6.41% <3.57%> (-0.20%)	⬇️

[rvagg]

@anorth @Stebalien @NemanjaLu92 I'd like to propose this replace #1999 and be merged as it is. It's essentially the same as #1999 but rebased on master and with a correct proofs dependency version. I've been using this for local testing but I'm keen to move us closer to a tag because cargo linking to the git repo for ref-fvm in filecoin-ffi is a bit of a nightmare thanks to the multiple versions.

[rvagg]

feedback addressed

[rvagg]

Also renamed all the NI-PoRep proofs types to be V1P2 rather than V1P1