drop 8.1 support, add 8.5

[brettmc]

Drop 8.1 support, and let rector upgrade the codebase with 8.2 as the minimum supported version

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.28%. Comparing base (26a2a4e) to head (b421999).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1857      +/-   ##
============================================
- Coverage     68.34%   68.28%   -0.06%     
  Complexity     3009     3009              
============================================
  Files           449      449              
  Lines          8798     8798              
============================================
- Hits           6013     6008       -5     
- Misses         2785     2790       +5     

Flag	Coverage Δ
8.2	68.24% <ø> (-0.04%)	⬇️
8.3	68.19% <ø> (-0.07%)	⬇️
8.4	68.22% <ø> (-0.05%)	⬇️
8.5	67.42% <ø> (-0.01%)	⬇️

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see 4 files with indirect coverage changes

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[brettmc]

NB that the upstream sury repo (which our developer image and shivammathur/setup-php use), doesn't have grpc yet, hence the two failures for 8.5

[cedricziel]

@brettmc rector config can also be adjusted :)

[brettmc]

rector config can also be adjusted :)

oh yeah, of course. That's an important missing step, thanks! :)

[Nevay]

Should also update CONTRIBUTING.md and Makefile.

[brettmc]

@open-telemetry/php-approvers I think this is ready. 8.5 is still waiting on https://codeberg.org/oerdnj/deb.sury.org/issues/68 I believe...

[intuibase]

@brettmc do we keep support for 12 months after "green" EOL or "orange" EOL?
https://www.php.net/supported-versions.php