minor #41080 Add a GitHub Action for tests against PHP 8.1 (derrabus, Nyholm)
minor #41080 Add a GitHub Action for tests against PHP 8.1 (derrabus, Nyholm)

This PR was merged into the 4.4 branch.

Discussion
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Add a GitHub Action for tests against PHP 8.1

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | N/A

I'd like to monitor our compatibility with the upcoming PHP 8.1 release. Because I failed miserably at convincing Travis to run our tests with PHP 8.1 (see #40532), I tried to do the same with GitHub Actions.

Commits
-------

6a328ae01e Update .github/workflows/tests.yml
6f1c4b8c58 PHP 8.1 must not cause the build to fail (yet)
b0b45105d7 Add _run_tests bash function
de4f0170e2 Add a GitHub Action for tests against PHP 8.1

ogizanagi/symfony,mpdude/symfony,stof/symfony,Taluu/symfony,Slamdunk/symfony,derrabus/symfony,sgehrig/symfony,stof/symfony,tucksaun/symfony,xabbuh/symfony,ro0NL/symfony,nicolas-grekas/symfony,HeahDude/symfony,oleg-andreyev/symfony,HeahDude/symfony,oleg-andreyev/symfony,damienalexandre/symfony,paradajozsef/symfony,Tobion/symfony,ro0NL/symfony,curry684/symfony,Tobion/symfony,d-ph/symfony,ogizanagi/symfony,curry684/symfony,symfony/symfony,mpdude/symfony,nicolas-grekas/symfony,zerkms/symfony,oleg-andreyev/symfony,xabbuh/symfony,ogizanagi/symfony,mpdude/symfony,symfony/symfony,damienalexandre/symfony,nicolas-grekas/symfony,sgehrig/symfony,tucksaun/symfony,symfony/symfony,mpdude/symfony,derrabus/symfony,Taluu/symfony,zerkms/symfony,paradajozsef/symfony,phramz/symfony,sgehrig/symfony,sgehrig/symfony,ro0NL/symfony,stof/symfony,xabbuh/symfony,tucksaun/symfony,oleg-andreyev/symfony,derrabus/symfony,d-ph/symfony,phramz/symfony,phramz/symfony,xabbuh/symfony,Slamdunk/symfony,d-ph/symfony,HeahDude/symfony,hhamon/symfony,d-ph/symfony,paradajozsef/symfony,ogizanagi/symfony,paradajozsef/symfony,curry684/symfony,Taluu/symfony,stof/symfony,HeahDude/symfony,derrabus/symfony,Taluu/symfony,zerkms/symfony,Tobion/symfony,ro0NL/symfony,hhamon/symfony,curry684/symfony,hhamon/symfony,damienalexandre/symfony,hhamon/symfony,zerkms/symfony,Slamdunk/symfony,Slamdunk/symfony,tucksaun/symfony,symfony/symfony,nicolas-grekas/symfony,damienalexandre/symfony,phramz/symfony,Tobion/symfony