Change error types to use core::error::Error

[jschillem]

With core::error::Error being stabilized in Rust 1.81, the error types no longer need to depend on std for this trait.

Removing this also renders the std unnecessary for any library consumers as the only usage of the std is now for test logging. Though it may make sense to leave the std flag to avoid breakages.

[briansmith]

Thanks!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.44%. Comparing base (c866e60) to head (cd54e96).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2871   +/-   ##
=======================================
  Coverage   96.44%   96.44%           
=======================================
  Files         204      204           
  Lines       20402    20407    +5     
  Branches      521      521           
=======================================
+ Hits        19676    19682    +6     
  Misses        602      602           
+ Partials      124      123    -1     

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[briansmith]

In addition to the change mentioned in the review, please squash the commits into a single commit, and update the commit message to remove "and removing the std feature".

[briansmith]

Thank you!