Remove librustzcash dependency

[joebebel]

Also removes FFI, updates Rseed to only be AfterZip212, adds test vectors to sync with latest librustzcash

[codecov-commenter]

Codecov Report

Merging #24 (2b3b8b7) into main (59bf5ca) will increase coverage by 8.73%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##             main      #24      +/-   ##
==========================================
+ Coverage   41.02%   49.76%   +8.73%     
==========================================
  Files          27       20       -7     
  Lines        2486     2552      +66     
==========================================
+ Hits         1020     1270     +250     
+ Misses       1466     1282     -184     

Impacted Files	Coverage Δ
masp_primitives/src/asset_type.rs	100.00% <ø> (ø)
masp_primitives/src/constants.rs	88.88% <ø> (ø)
masp_primitives/src/keys.rs	43.33% <ø> (ø)
masp_primitives/src/redjubjub.rs	59.45% <ø> (-1.26%)	:arrow_down:
masp_primitives/src/sapling.rs	45.45% <ø> (ø)
masp_proofs/src/circuit/convert.rs	62.85% <ø> (ø)
masp_proofs/src/circuit/pedersen_hash.rs	77.50% <ø> (ø)
masp_proofs/src/lib.rs	0.00% <ø> (ø)
masp_primitives/src/primitives.rs	83.33% <25.00%> (+14.44%)	:arrow_up:
masp_primitives/src/merkle_tree.rs	45.60% <25.58%> (-2.22%)	:arrow_down:
... and 15 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 59bf5ca...2b3b8b7. Read the comment docs.

[XuyangSong]

I've added the ffi implementation for convert in branch add_convert_params. Could we merge #25 first in case we could leave the history?

[joebebel]

OK, let's merge #25 first. Then let's remove the FFI in a separate commit, then merge this PR last. Otherwise the commit history is hard to read because of the deletion.