[Generator][SemanticSequencer] Dead Assignments

Depending on the situation, Xtext will create dead assigments inside the generated SemanticSequencer.

e.g.

@Override
	public void sequence(ISerializationContext context, EObject semanticObject) {
		EPackage epackage = semanticObject.eClass().getEPackage();
		ParserRule rule = context.getParserRule();
		Action action = context.getAssignedAction();
		Set<Parameter> parameters = context.getEnabledBooleanParameters();
                ....

in this case rule, action and parameters are unused.

Example Grammar

MyRoot:
	r1=Root1 | r2=Root2
;

Root1:
	"root1" name=ID
;

Root2:
	"root2" name=ID
;

or

MyRoot:
	r1=Root1
;

Root1:
	"root1" name=ID
;

Start with the generated SemanticSequencer output described in the issue and reproduce the examples using the provided grammars. Trace the generator path that emits sequence(...) and identify when rule, action, and parameters are unused. Done means generated sequencers no longer contain dead assignments for these cases, with coverage for both example grammars.