Utilize leftover dust in conversions.

[murisi]

Describe your changes

An attempt to address the reported bug where users' MASP balances are potentially underestimated. This bug is caused by compute_exchanged_amount not attempting to consolidate dust and apply conversions on that. This PR attempts to address this issue by always bringing relevant dust back into input before attempting a conversion. Under the assumption that the ledger's current epoch does not change during applying conversions, this code algorithm should terminate because:

• If no conversions at all apply to the consolidated amount (i.e the principal plus the dust), then the consolidated amount is simply moved to output (so that output is greater than before) progressing the loop in the process
• If a conversion does apply, then the consolidated amount is converted into something "better" and the dust left from this conversion is left in output again. Hence the (one-way) conversion progresses the loop.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 74.03%. Comparing base (1465f26) to head (c97f79d).
Report is 71 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4287      +/-   ##
==========================================
- Coverage   74.03%   74.03%   -0.01%     
==========================================
  Files         345      345              
  Lines      110047   110046       -1     
==========================================
- Hits        81476    81472       -4     
- Misses      28571    28574       +3     

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