gossip: Resolve Rust 1.88 clippy lints and format strings

[steviez]

Problem

Working towards #6850, broken out from #6854

Summary of Changes

• Run cargo clippy --fix --tests with Rust 1.88.0 set in rust-toolchain.toml
  • These should only be instances of uninlined_format_args
• Run cargo fmt with format_strings = true set in rustfmt.toml

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 71.79487% with 11 lines in your changes missing coverage. Please review.

Project coverage is 83.2%. Comparing base (6bc9fb1) to head (9854e13).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6972   +/-   ##
=======================================
  Coverage    83.2%    83.2%           
=======================================
  Files         856      856           
  Lines      376426   376440   +14     
=======================================
+ Hits       313321   313333   +12     
- Misses      63105    63107    +2     

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[gregcusack]

lgtm! thank you!