Release checklist for 2.0.16

[jrfnl]

PRs to cherrypick into the next 2.0.x release (if there will be one):

• GH Actions: add actionlint job #925
• Move shell scripts into dedicated directory #928
• GH Actions: improve "don't run on forks" condition #935
• README: add license badge #936
• GH Actions: update PHP ini configuration #939
• PHP 8.5 | Tests: prevent deprecation notice for Reflection*::setAccessible() #940
• GH Actions: Bump actions/download-artifact from 4 to 5 #942
• Corrected URL of the Request Python library URL in README.md #944
• GH Actions: Bump actions/checkout from 4 to 5 #945
• PHP 8.5: Prevent deprecation notices for curl_close #947
• GH Actions: Bump actions/setup-python from 5 to 6 #948
• GH Actions: "pin" all action runners  #951
• 🔏 Update certificate bundle #954
• Composer: update PHPUnit Polyfills #955
• PHP 8.5 | Fix various "Using null as an array offset" deprecation notices #956
• Composer: remove roave/security-advisories #961
• GH Actions: split "update-cacert" workflow #962
• GH Actions: allow test runs to succeed on fork #964
• GH Actions/test: use the latest Python version for mitmproxy #965
• Fix tests for expired and revoked SSL certificates #967
• PHP 8.5 | FilteredIterator: do not accept objects #968
• GH Actions: Bump actions/upload-artifact from 4.6.2 to 5.0.0 #974
• GH Actions: Bump actions/download-artifact from 5.0.0 to 6.0.0 #975
• GH Actions: do not persist credentials #980
• GH Actions: update for the release of PHP 8.5 #981