Murisi/mock masp prover

[murisi]

Describe your changes

Replaced the test fixture saving system with a mock MASP prover and verifier system. More specifically:

• Repurposed the mock transaction prover (used to generate arbitrary transactions fast) for the MASP client
  • This prover is identical to the real one except that it generates fake proofs in order to save time
• Wrote a mock MASP verification context that is identical to the real one except that it assumes correct proofs
  • This is necessary because the real verification context would always reject transactions from the mock prover
• When the testing flag is enabled, the mock prover and verifier are now activated instead of the real ones
• Removed the test fixture directory and the variations of the test-integration command

The advantages/drawbacks of the above system are as follows:

• Generation of new (never before saved) MASP transactions is much faster (a few seconds)
  • This means that it is much quicker to test changes to the MASP client or integration tests
• Test fixtures no longer have to be saved in the repository
• Less make targets are required for testing the MASP client
• Drawback is that proofs are no longer verified in testing, hence proof verification must be tested elsewhere

Indicate on which release or other PRs this topic is based on

Namada 0.31.5
anoma/masp#72

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 159 lines in your changes are missing coverage. Please review.

Project coverage is 53.34%. Comparing base (c733be2) to head (93b92c7).
Report is 79 commits behind head on main.

Files	Patch %	Lines
crates/sdk/src/masp.rs	0.00%	159 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2695      +/-   ##
==========================================
- Coverage   53.38%   53.34%   -0.04%     
==========================================
  Files         302      302              
  Lines      103403   103469      +66     
==========================================
- Hits        55198    55196       -2     
- Misses      48205    48273      +68     

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