Test enabling rewards after shielding and large amounts in the masp

[sug0]

Describe your changes

Based on #3954 (DIFF)
Rebases commits from #3954, therefore it essentially supersedes it.

This PR accomplishes the following:

• Fixes clippy lints
• Fixes formatting
• Adds new storage functions to update the masp token map
• Adds a new masp integration test to check the behavior of enabling rewards on some asset that had already been shielded
• Adds a new masp integration test to check the behavior of interacting with tokens in the masp whose values span across multiple notes (because to represent them we need more than 64 bits)
• Adds a new masp integration test to check the behavior of initializing the token map with null rewards, shielding, then updating the rewards to some non-null value
• Modified change computation to deal with each individual masp denomination separately

To check the rest of the changes, check the description of #3954.

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:

[murisi]

This is a review of just 1f05f77 . I think this approach is the way to go, thanks! Ah, I see the new MASP integration test is still failing. Let me see if I can spot the error...

My guess is that this issue is similar to having a shielded balance with the single note 1 [2^64 Wei] and trying to spend/send 1 [2^0 Wei] to another payment address. Though these two asset types concern the same underlying token, they are not convertible, and the MASP cannot use/break down the former amount (as far as I remember) to send the much smaller output. You would first need to unshield the 1 [2^64 Wei] note to get a transparent balance of 2^64 Wei, and then shield (2^64 - 1) [2^0 Wei] back to yourself and the other 1 [2^0 Wei] to your desired destination. So essentially the Insufficient funds error would be correct in a sense. This is my guess based on how this test also broke #3954 ...

If the above guess is correct, then the resolution to this error is to adjust the amounts worked with in the new test to stop straddling the MASP digit boundaries. Or more adventurously, do the unshield-then-shield trick above. But I would lean towards the former solution and make a separate test to demonstrate the above inconvertibility behaviour.

[codecov]

Codecov Report

Attention: Patch coverage is 89.28571% with 33 lines in your changes missing coverage. Please review.

Project coverage is 73.94%. Comparing base (a148ac3) to head (6cd9e94).
Report is 31 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/shielded_token/src/masp/shielded_wallet.rs	93.69%	15 Missing ⚠️
crates/core/src/token.rs	62.50%	6 Missing ⚠️
crates/sdk/src/lib.rs	0.00%	5 Missing ⚠️
crates/core/src/uint.rs	83.33%	4 Missing ⚠️
crates/sdk/src/args.rs	0.00%	2 Missing ⚠️
crates/sdk/src/tx.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3959      +/-   ##
==========================================
- Coverage   73.99%   73.94%   -0.05%     
==========================================
  Files         341      341              
  Lines      106614   106450     -164     
==========================================
- Hits        78888    78715     -173     
- Misses      27726    27735       +9     

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[sug0]

@brentstone I think this PR might require some docs changes, because it changes the behavior of --disposable-gas-payer

[batconjurer]

Understatement of the year. Bertha has all of the tokens! 🤣

[batconjurer]

dayum