Remove Rascal search path contribution feature

[toinehartman]

Describe the bug

On every operation on a Rascal search path, the complete search path is rebuilt in RascalSearchPath::collect:

rascal/src/org/rascalmpl/interpreter/load/RascalSearchPath.java

Lines 106 to 113 in 16abf95

	public List<ISourceLocation> collect() {
	List<ISourceLocation> paths = new LinkedList<ISourceLocation>();
	for (IRascalSearchPathContributor c : contributors) {
	c.contributePaths(paths);
	}
	return paths;
	}

The path cannot be simply built once, because the search path can be amended after the evaluator has been initialized. However, in a typical scenario, the search path is set up before any operations on the search path. Hence, the result of collect() could be re-used and only invalidated on changes to the search path, to greatly reduce the number of collections being built.

[DavyLandman]

We tend to avoid adding caches unless we find stuff in a profile that really pops out. So is this showing up in a profile?

[jurgenvinju]

This was set up like this such that changes in the IDE environment could be reflected dynamically. Specifically in Eclipse, but I guess this is also useful for other contexts.

However, the entire path contributor feature is not used at this moment. We only add the libs and the target folder and that's it. The whole abstraction has become unnecessary. I'd rather clean it up completely than cache it.