Fix nullifiers check

[grarco]

Describe your changes

Closes #2594.

Call valid_nullifiers_reveal regardless of the transaction source to make sure that a shielding tx doesn't reveal any nullifier. Enforces that at least one shielded input is present if the source of the tx is the MASP.

Refactors the checks on the bundles and fixes the check on the shielded outputs when the target is MASP which was previously wrong (was not taking into account the case in which shielded_outputs was None.

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

v0.33.0

Checklist before merging to draft

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 38 lines in your changes are missing coverage. Please review.

Project coverage is 59.40%. Comparing base (97ec5b4) to head (f77324a). Report is 4 commits behind head on main.

Files	Patch %	Lines
crates/namada/src/ledger/native_vp/masp.rs	0.00%	38 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2621   +/-   ##
=======================================
  Coverage   59.39%   59.40%           
=======================================
  Files         298      298           
  Lines       92771    92771           
=======================================
+ Hits        55104    55107    +3     
+ Misses      37667    37664    -3     

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