declare internal dev-dependencies via path (backport #4345)

[mergify]

This is a workaround for rust-lang/cargo#4242

Describe your changes

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:

---

This is an automatic backport of pull request #4345 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.19%. Comparing base (c934e9f) to head (f969d8f).
Report is 2 commits behind head on maint-libs-0.47.

Additional details and impacted files

@@               Coverage Diff                @@
##           maint-libs-0.47    #4346   +/-   ##
================================================
  Coverage            74.18%   74.19%           
================================================
  Files                  345      345           
  Lines               110632   110632           
================================================
+ Hits                 82076    82079    +3     
+ Misses               28556    28553    -3     

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