thread-manager: 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 40.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 83.2%. Comparing base (64382a5) to head (aa0f8a0).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master    #7088     +/-   ##
=========================================
- Coverage    83.3%    83.2%   -0.1%     
=========================================
  Files         854      854             
  Lines      374711   374713      +2     
=========================================
- Hits       312197   312109     -88     
- Misses      62514    62604     +90     

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[alexpyattaev]

Thank you!