rustfmt: Run on the routing directory (3/3)

[tnull]

Based on #3337.

This is PR 3/3, formatting the rest of routing.

[codecov]

Codecov Report

Attention: Patch coverage is 95.94203% with 42 lines in your changes missing coverage. Please review.

Project coverage is 89.85%. Comparing base (a0d0f02) to head (8a8e6fa).
Report is 1335 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/routing/utxo.rs	92.12%	34 Missing and 5 partials ⚠️
lightning/src/routing/test_utils.rs	99.44%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3338      +/-   ##
==========================================
+ Coverage   89.65%   89.85%   +0.19%     
==========================================
  Files         126      126              
  Lines      102750   106502    +3752     
  Branches   102750   106502    +3752     
==========================================
+ Hits        92123    95695    +3572     
- Misses       7904     8115     +211     
+ Partials     2723     2692      -31     

Flag	Coverage Δ
	89.85% <95.94%> (+0.19%)	⬆️

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[joostjager]

This command may be a good way to decide on the timing for this PR. Look for all open prs that touch a file:

~/repo/rust-lightning (merge-scores ✔) gh pr list -L 1000 --json url,files | jq 'map(select(.files | map(.path | contains("scoring.rs")) | any)) | map(.url)'

[
  "https://github.com/lightningdevkit/rust-lightning/pull/3562",
  "https://github.com/lightningdevkit/rust-lightning/pull/3422",
  "https://github.com/lightningdevkit/rust-lightning/pull/3386",
  "https://github.com/lightningdevkit/rust-lightning/pull/3338",
  "https://github.com/lightningdevkit/rust-lightning/pull/2927",
  "https://github.com/lightningdevkit/rust-lightning/pull/2793"
]

Most seems to be draft or small prs, so maybe not a bad time?

This is just scoring.rs though, but can adapt query.

[tnull]

Closing in favor of doing fn-level rustfmt::skip first.