java.net.URI.toURI broken

[cyrille-artho]

The model class implements toURI, but this function was not tested with a unit test. We therefore need a unit test and then a fix.

1. Create a unit test that constructs a simple URI from a File with a String that has the right URI syntax.

2. Look into ways to obtain a working URI by fixing a dependency in the JPF model classes, most likely by adding setJavaNetURIAccess, which is probably going to resemble setJavaNetURLAccess.

Also look into the class description JavaDoc of src/classes/modules/java.base/jdk/internal/misc/SharedSecrets, which still refers to Java 1.5/Java 6 and is therefore seriously outdated.

If the model class for SharedSecrets can indeed be removed, we want a careful review of its use of Unsafe and whether removal might cause problems later.