feat!: respect NO_COLOR environment variable in colored feature

[haraldmaida]

no-color.org specifies that CLI-tools should uniformally respect the NO_COLOR environment variable before anything is printed in colors to the terminal.

The "highlight diffs" feature has been enhance to respect the NO_COLOR environment variable and configured color-mode is overruled and no colors are printed to the terminal.

BREAKING CHANGE:

This is somehow a breaking change, not of the API, but of the behavior.

[codecov]

Codecov Report

Attention: Patch coverage is 95.83333% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.05%. Comparing base (2fe5634) to head (308ee85).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/colored/mod.rs	95.83%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
- Coverage   94.05%   94.05%   -0.01%     
==========================================
  Files          24       24              
  Lines        2272     2288      +16     
  Branches     2272     2288      +16     
==========================================
+ Hits         2137     2152      +15     
- Misses        129      130       +1     
  Partials        6        6              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.