ConfigurationActivator should lazy load the PlatformConfiguration

[laeubi]

Currently ConfigurationActivator eagerly loads and creates PlatformConfiguration, as this involves scanning a lot of jar files I noticed this becomes quite slow on Windows.

As the field is only read when calling ConfigurationActivator.getBundleGroups() the creation and initialization of the object should be handled there to shift the penalty to the place where it is actually required, callers can then for example benefit from the UI and inform the user that something is in progress instead of blocking the OSGi Startup in general, whether or not the information is used at all.

This might not be noticeable in a regular IDE if the windows defender exclusion is in place or might depend on other factors but seems easy enough to improve the situation for example custom RCP application.