Fix caching of task ext properties with the strict parser

[bentsherman]

Close #6695

This PR updates the strict parser to collect references to task.ext.* so that they are added to the task hash (docs).

I originally thought to move the VariableVisitor into nf-lang so that it is re-used by both, but I think this visitor does a lot of unnecessary work, and I didn't want to alter the old parser too much, so I just created a separate implementation for the strict parser that is much simpler. It only collects references to task.ext.* instead of all variable references.

Note to self: once we make the strict parser the default (#6643), we should revisit the runtime layer and how it handles these variable references. I think it could be simplified quite a bit.

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[jorgee]

The reverse in last statement is reversing the full stringbuilder getting something like ksat.txe.sgra. I think you wanted to just reverse the order of elements of a list of strings and join with . later.

Suggested change

	private static String asPropertyChain(PropertyExpression node) {
	var builder = new StringBuilder();
	builder.append(node.getPropertyAsString());
	var target = node.getObjectExpression();
	while( target instanceof PropertyExpression pe ) {
	builder.append('.');
	builder.append(pe.getPropertyAsString());
	target = pe.getObjectExpression();
	}
	builder.append('.');
	builder.append(target.getText());
	return builder.reverse().toString();
	}
	private static String asPropertyChain(PropertyExpression node) {
	var list = new ArrayList<String>();
	list.add(node.getPropertyAsString());
	var target = node.getObjectExpression();
	while( target instanceof PropertyExpression pe ) {
	list.add(pe.getPropertyAsString());
	target = pe.getObjectExpression();
	}
	list.add(target.getText());
	Collections.reverse(list);
	return String.join(".", list);
	}