[PHP 8.4] Use SessionHandlerInterface instead of Zend_Session_SaveHandler_Interface

[sgiehl]

Description:

PHP 8.4 will deprecate the legacy signature of session_set_save_handler. Passing more than 2 parameters to the method will then trigger a deprecation notice.

To fix this the PR will replace the usage of Zend_Session_SaveHandler_Interface with the PHP built in interface SessionHandlerInterface, which can be directly passed to session_set_save_handler. This already exists since PHP 5.4, so should be compatible with all PHP versions we support.

For this the original Zend Session classes have been adjusted.

See https://php.watch/versions/8.4/session_set_save_handler-alt-signature-deprecated

refs #22471

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed

[michalkleiner]

I'm wondering whether we could direct all PHP 8.4 related PRs into a separate PHP 8.4 compatibility branch and then merge it all at once when all the adjustment work is done? Mainly to avoid merging in stuff that will pass on 5.x against 8.3 but we won't have immediate tests feedback on 8.4

[sgiehl]

@michalkleiner The changes of this PR are currently also in #22667, where the tests are only running with 8.4 and are passing. But I had to disable deprecations there, as the tests didn't pass with deprecations enabled.