add PHPUnit 12 compatibility; typos; PHP 8.4 compatibility; some cleanup; drop PHP 7.4

[haeber]

See #647 .

[alexislefebvre]

Thanks for your work.

Could you please split this PR and open a second PR with only Markdown and code comment changes?

[alexislefebvre]

We should test (later) if this is still necessary.

[alexislefebvre]

Thanks!

I merged it as is. If you contribute again, please split the changes, ideally in several PRs, or at least in several commits, to ease reviewing.

Here is the release with these changes: https://github.com/liip/LiipFunctionalTestBundle/releases/tag/4.14.0

[haeber]

Thanks!

I merged it as is. If you contribute again, please split the changes, ideally in several PRs, or at least in several commits, to ease reviewing.

Here is the release with these changes: https://github.com/liip/LiipFunctionalTestBundle/releases/tag/4.14.0

Thanks a lot, actually I read your message and wanted to split the PR into 2 PRs, but my time was up and I had to commute home (and therefore wanted to do it tomorrow). But thanks for the hint, I will split the next change directly from the start, if it has multiple changes.