assorted clippy cleanups

[imp]

Few incremental clippy cleanups (no functionality change)
All the changes are grouped by the lint they address.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.3%. Comparing base (2d02f44) to head (f44e39e).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
kube-core/src/error_boundary.rs	0.0%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1825     +/-   ##
=======================================
+ Coverage   76.3%   76.3%   +0.1%     
=======================================
  Files         84      84             
  Lines       7899    7897      -2     
=======================================
  Hits        6024    6024             
+ Misses      1875    1873      -2     

Files with missing lines	Coverage Δ
kube-client/src/client/builder.rs	71.7% <100.0%> (ø)
kube-client/src/client/client_ext.rs	85.9% <100.0%> (-0.2%)	⬇️
kube-runtime/src/scheduler.rs	96.1% <100.0%> (ø)
kube-core/src/error_boundary.rs	73.7% <0.0%> (ø)

... and 3 files with indirect coverage changes

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[clux]

appreciate it!