(SplitPackageBinding)

- replace remaining PlainPackageBinding constructor invocations
- putting packages into ModuleBinding.declaredPackages in
ModuleBinding.addPackage is then not needed, after removing it,
remaining
functionality can be inlined
- removed some unnessary code in MB.getVisiblePackage from the time when
declaredPackages could contain SplitPackageBindings
- always put into cache in MB.getVisiblePackage and remove cache
handling from getTopLevelPackage

Change-Id: Ibd7bddebff4e0315f0f08a5486acd714bc3c46f8