CMake: use params for DefineCAmkESVMFileServer()

[axel-h]

Use the new version of DefineCAmkESVMFileServer() that accpts files as parameters. This allows doing everything in one call.

This needs at least seL4/camkes-vm#31 to get the functionality, but must also work with seL4/camkes-vm#76 that removes the obsolete CMake function AddToFileServer().

Test with: seL4/camkes-vm#76, seL4/seL4_tools#151

[axel-h]

Can we merge this, now that seL4/camkes-vm#31 has been merged?

Note that As a side effect, this stops using the CMake wrapper function DeclareCAmkESVMRootServer() now, as it lacks the options to pass the necessary file server parameters. In the long run, I think it would be worth deprecating this wrapper function and require all projects calling DefineCAmkESVMFileServer() and DeclareCAmkESRootserver() explicitly in their CMake files. It is a bit less convenient, but it makes it much more more transparent, what is really happening.
The alternative would be giving the wrapper DeclareCAmkESVMRootServer() more file server parameters. But I do not think going is road is really helpful, as this causes a convenience function to get overloaded with parameters, which all need to be explained again and could be more confusing in the end.