add tests & refactor tx crate

[tzemanovic]

Describe your changes

related to #1497

closes #3200

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 80.30994% with 216 lines in your changes missing coverage. Please review.

Project coverage is 73.00%. Comparing base (be38d4c) to head (59f89bf).
Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/tx/src/section.rs	69.00%	137 Missing ⚠️
crates/sdk/src/signing.rs	4.16%	23 Missing ⚠️
crates/tx/src/sign.rs	80.99%	23 Missing ⚠️
crates/tx/src/types.rs	97.27%	12 Missing ⚠️
crates/node/src/shell/finalize_block.rs	37.50%	5 Missing ⚠️
crates/sdk/src/masp.rs	0.00%	3 Missing ⚠️
crates/vote_ext/src/lib.rs	66.66%	3 Missing ⚠️
crates/governance/src/vp/mod.rs	50.00%	2 Missing ⚠️
crates/node/src/shell/mod.rs	33.33%	2 Missing ⚠️
crates/trans_token/src/vp.rs	50.00%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3835      +/-   ##
==========================================
+ Coverage   72.82%   73.00%   +0.18%     
==========================================
  Files         338      339       +1     
  Lines      104220   104637     +417     
==========================================
+ Hits        75897    76393     +496     
+ Misses      28323    28244      -79     

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[grarco]

🤣

[grarco]

If this was an owned value instead of a ref we could use InnerTx inside both BatchedTx and BatchedTxRef in place of TxCommitments but this would imply many more changes and those two struct are only used within the protocol, don't know if you have a strong opinion on this

[grarco]

Also there are a few functions in tx/src/data/mod.rs that take as an input a reference to the commitments using Either

namada/crates/tx/src/data/mod.rs

Line 172 in 760462b

commitments: Either<&Hash, &TxCommitments>,

I think we can use the new InnerTxRef now