Upgrade dependencies and set minimal PHP version to 7.4

[cedric-anne]

Purpose of this pull request is to be able to use sabre/dav in combination wih latest versions of other sabre components into a same project.

I aligned PHP requirements (PHP 7.4 -> 8.2), but maybe we can drop here support of PHP 7.4.

Before releasing a new 5.0 version, code should probably modernized (for instance by adding return types, parameters type hinting, ...), but this would be part of another PR.

[cedric-anne]

Not sure about hox to fix the error shown in test suite. If I add a return type to the method Sabre\DAV\Xml\Property\Complex::xmlDeserialize(), it will result in following error: TypeError: Sabre\DAV\Xml\Property\Complex::xmlDeserialize(): Return value must be of type Sabre\Xml\Element\XmlFragment, string returned

[cedric-anne]

@phil-davis

I think I will not be able to finish this task. Main problem here is that return types of Sabre\DAV\Xml\Property\Complex::xmlDeserialize() and Sabre\DAV\Xml\Property\ResourceType::xmlDeserialize() are not compatible with the definition in extended class. Changing it has many side effects and I do not know how to manage it.

[phil-davis]

I need to keep moving with my voluntary work on sabre-io/vobject#591 and get a major version published there. Then all the sabre-io/dav dependencies will have new major versions that support only PHP 7.4 and up. Then "we" (whoever can provide effort) can work on the same for sabre-io/dav

[cedric-anne]

I wanted to help on this point, but I do not know the project well enough to carry out this first step.

I close this PR, maybe I will be able to help better when someone who knows the project better takes over the job.