Issue Description:

Need to implement DrlExprParser to parse constraints. It is required in drools engine.

Probably by splitting parser rules to ConstraintParser.g4 with a new VisitorImpl.

Copy these test classes from drools repo's test-compiler-integration.

DRLExprParserTest
DescrDumperTest

Acceptance Criteria:

• Able to apply the DrlExprParser to drools engine and continue DROOLS-7591