Allow jakarta.security.jacc.PolicyConfigurationFactory.provider as context parameter

[arjantijms]

The system property with name "jakarta.security.jacc.PolicyConfigurationFactory.provider" is used to set an alternative PolicyConfigurationFactory in Jakarta Authorization. This parameter is however not always easy to set (depending on how much the runtime is under the control of the deployer) and its basically undefined where exactly the class that the property references should live.

On the (archived) mailing list we discussed at the time alternatives to this, and suggested to use a deployable artefact for this. At the time a RAR was proposed, but since then the emphasis has shifted away from RAR and JAR deployments, to mostly WARs.

As such we can introduce a web.xml context parameter that is treated the same as the system property, but takes precedence, and loads the PolicyConfigurationFactory using the web archive's class loader.