Test MASP inverse conversions

[grarco]

Describe your changes

Depends-on: #4146 (diff: https://github.com/anoma/namada/pull/4193/files/9f1d17825350c9d7ce9e0b2864a0ce74d9ac7c8c..43974e6d6e3b13c2e856199c493757e7dc963ce7)

Adds tests for the MASP inverse conversions.

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

[codecov]

Codecov Report

Attention: Patch coverage is 98.02555% with 17 lines in your changes missing coverage. Please review.

Project coverage is 74.66%. Comparing base (be0e81f) to head (43974e6).
Report is 31 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/shielded_token/src/masp/shielded_wallet.rs	98.02%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4193      +/-   ##
==========================================
+ Coverage   74.48%   74.66%   +0.17%     
==========================================
  Files         341      341              
  Lines      107710   108469     +759     
==========================================
+ Hits        80227    80987     +760     
+ Misses      27483    27482       -1     

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[brentstone]

Should this be merged now?