[new-parser] Unify error reporting of DRLParser and DRL6Expressions

[yurloc]

DRL6Expressions is a bit ahead of DRLParser so I take that as a benchmark.

Impl

The code that registers error listeners is very different for both parsers. It could be unified and reused.

API

Contents of parser.getErrors() should be unified.

DRL6Expressions

org.drools.drl.parser.DroolsParserException: [ERR 102] Line 1:1 mismatched input '<EOF>' expecting {...}

DRLParser

org.drools.drl.parser.ParserError: [18,0]: mismatched input 'impot' expecting {...}

So while the problem occurs during parsing (mismatched input), parsers report different exception types with slightly different messages. This should be unified.

Tests

• DRL6Expressions has error reporting test coverage in org.drools.drl.parser.antlr4.DRLExprParserTest#testMismatchedInput and other test methods.
• DRLParser should receive equal test coverage.