Should NameEnvironment.computeClasspathLocations() consider the release also for source locations?

Method `NameEnvironment.computeClasspathLocations(IWorkspaceRoot, JavaProject, Map, int)` may use the `releaseTarget` to
* distinguish modular / non-modular builds
* filter output folders
* select the correct module-info.java (with #4534)

I would think that also `sourceLocations` should be filtered in MR projects. This should then be done before any ModulePathEntry is created (which holds a reference to all applicable source locations).

Start at NameEnvironment.computeClasspathLocations(IWorkspaceRoot, JavaProject, Map, int) and trace how releaseTarget and sourceLocations are handled before any ModulePathEntry is created. Done means source locations in multi-release projects are filtered for the selected release while the existing modular, output-folder, and module-info handling remains correct.

Written by the indexing model from the issue text.