feat: drop support for php < 8.1, drop support for symfony < 5.4 (WIP)

[Chris53897]

https://github.com/php-http/client-common/issues/242

Just a quick view and open for disussion what to do next. Needs rebasing after the other 2 PRs are merged.

Checklist

• [x] Updated CHANGELOG.md to describe BC breaks / deprecations | new feature | bugfix
• [] Documentation pull request created (if not simply a bugfix)

To Do

• [ ] to Discuss