Fix offline wrapper signature by elsewho

[grarco]

Describe your changes

Fixes offline wrapper signatures and adds two new tests for this. The bug was only affecting offline wrapper signing when the signer did not own the keys to also sign the inner transaction:

• Once the inner tx had been dumped and signed offline the user had to reload the tx, wrap it and dump the wrapper
• At this point they needed to produce the signature for the wrapper offline. To do so, they needed to pass to the offline signing command both the serialized wrapper and the inner signatures (that were not attached to the tx when wrapped), but the command does not accept serialized signatures, just signing keys. So this flow was only possible if the wrapper signer also owned the keys to sign the inner transactions (effectively producing the inner signatures a second time)

The tx command now attaches the raw signatures to the tx when a --dump-wrapper-tx is requested to allow for a different wrapper signer.

The offline sign command and the custom tx one now return errors if a wrapper singer/signature is provided but the tx is not a wrapper.

Also removes a redundant sign-tx client command.

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 28.57143% with 5 lines in your changes missing coverage. Please review.

Project coverage is 74.58%. Comparing base (9f817f0) to head (25c2564).
Report is 56 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/sdk/src/tx.rs	28.57%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4120   +/-   ##
=======================================
  Coverage   74.58%   74.58%           
=======================================
  Files         341      341           
  Lines      107491   107502   +11     
=======================================
+ Hits        80171    80184   +13     
+ Misses      27320    27318    -2     

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