feat: Turn the PSR-0 sessionhandler into a SessionHandlerInterface and register in object form

[ralflang]

Traditionally a custom sessionhandler would be registered as a set of individual functions or methods. This is now deprecated.
The preferred method is now to implement the SessionHandlerInterface with a class and register an object of this class.

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

[ralflang]

@TDannhauer Example of a PR where I did not touch any metadata. After merge I ran the "horde-components release h6" tool.
See this: 570496d

It generates the changelog from the commit message. Commits without conventionalcommit syntax are ignored.
It updates the version string in all sorts of places.

It updates the composer.json date and notably removes the horde-installer-plugin (it used to be hardcoded for all horde libraries but we only need it for bundles, applications, themes and libraries with js files)

The first time it runs on an "old style" repo it does some extra stuff.

• remove package.xml
• remove old CHANGES file
• move changelog.yml file from doc/foo/bar/baz to doc/
• reformat the changelog.yml file from some frequent mishaps and fix logical errors (i.e. an alpha version cannot be marked as "stable"

Finally it does some extra steps:

• commit
• tag
• push

Things it doesn't do yet

• Try a validation install
• Create a Github Release
• Run box if the box config file is present. Box is a compiler which combines a cli script with all its dependencies into a single ready to run file.
• Update/fix pipeline and tool configuration files