chore: Expand dependabot coverage

[neilconway]

Which issue does this PR close?

• N/A

Rationale for this change

This PR tweaks the dependabot config to send dependency updates for a few parts of the repo that were previously missed:

• dev/depcheck is excluded from the Cargo workspace and has its own Cargo.lock (chore: Update depcheck toolchain and dependencies #24289 updates the dependencies manually as an interim fix)
• datafusion/wasmtest/datafusion-wasm-app has its own npm package-lock.json
• Composite actions under .github/actions/
• The Python dependencies are a uv workspace rooted at the top-level pyproject.toml with a shared uv.lock, but only docs/ was covered — dev/ and benchmarks/ got no version updates.

What changes are included in this PR?

• Add a cargo entry for /dev/depcheck
• Add an npm entry for /datafusion/wasmtest/datafusion-wasm-app
• Change the github-actions entry from directory: "/" to directories: ["/", "/.github/actions/*"] so composite actions are covered
• Replace the pip /docs entry with a uv entry at the repository root, covering the whole uv workspace and uv.lock

Are these changes tested?

Some manual testing, hard to really test exhaustively without letting dependabot run.

Are there any user-facing changes?

No.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.29%. Comparing base (9b3b518) to head (73e2cb1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24290      +/-   ##
==========================================
- Coverage   81.29%   81.29%   -0.01%     
==========================================
  Files        1110     1110              
  Lines      385336   385336              
  Branches   385336   385336              
==========================================
- Hits       313261   313253       -8     
- Misses      53594    53598       +4     
- Partials    18481    18485       +4     

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