replace E_USER_ERROR triggers with RuntimeExceptions

The use of trigger_error with a E_USER_ERROR is deprecated in PHP 8.4

do not call get_class() without a parameter

This has been deprecated in PHP 8.3

code style: line breaks

Apply rector fixes to inc/Extension and inc/Debug

Refactor deprecation logging into its own class

This gives us the flexibility to handle both deprecated properties and
methods/functions properly.

Use deprecation helper

Instead of writing our own magic getters and setters for all variables
that used to be public, this adds a trait that does that in a generic
way.
This trait was copied from Me

Use deprecation helper

Instead of writing our own magic getters and setters for all variables
that used to be public, this adds a trait that does that in a generic
way.
This trait was copied from MediaWiki and adjusted to DokuWiki.
The original author seems to be @tgr Tisza Gergő

The downside of this trait is that the properties keep their
(potentially undesired) name. While that could be fixed within the
helper, that might add unnecessary complexity. The name can change when
support is dropped.

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