chore: Bump MSRV to 1.82

[larseggert]

And address some TODOs that were enabled by the new MSRV.

[codecov]

Codecov Report

Attention: Patch coverage is 98.68421% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.72%. Comparing base (d686c47) to head (ee7c483).

Files with missing lines	Patch %	Lines
src/linux.rs	97.14%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #91      +/-   ##
==========================================
+ Coverage   86.53%   86.72%   +0.19%     
==========================================
  Files           5        5              
  Lines         557      565       +8     
  Branches      557      565       +8     
==========================================
+ Hits          482      490       +8     
  Misses         49       49              
  Partials       26       26              

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[larseggert]

OpenBSD's Rust package is 1.81. NetBSD and FreeBSD hit rust-lang/rust#137640.