* Clean up

* Simplify MultiCurl execution loop

- Removes legacy workarounds
- Deprecates MultiCurl::setRequestTimeAccuracy()
- Removes use of CURLM_CALL_MULTI_PERFORM ("As of cURL 7.20.0, this constant is not used")

* Add PHP 8.5 to continuous integration tests

* Use variable

* Add temporary skip

* Allow PHP CS Fixer to run on unsupported PHP versions

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Zach Borboa <zachborboa@gmail.com>

* Use WeakMap for active handle tracking

- Replaces array-based tracking with PHP 8.0 \WeakMap
- Replaces an O(N) lookup with an O(1) lookup in the MultiCurl execution loop

* Fix tests