Improve duplicate DSL methods suffix error message

[bd82]

Error: Parser Definition Errors detected:
->OPTION<- with numerical suffix: ->0<-
appears more than once (2 times) in the top level rule: ->mediaList<-.
Also note that numerical suffix 0 means OPTION without any suffix.
To fix this make sure each usage of OPTION
in the rule ->mediaList<- has a different occurrence index (0-5), as that combination acts as a unique
position key in the grammar, which is needed by the parsing engine.
For further details see: https://sap.github.io/chevrotain/docs/FAQ.html#NUMERICAL_SUFFIXES

The Also note that numerical suffix 0 means OPTION without any suffix. is redundant as we can distinguish between explicit and implicit suffixes in the GAST

[bd82]

It now look like this:

Error: Parser Definition Errors detected:
->SUBRULE1<- with argument: ->anotherRule<-
appears more than once (2 times) in the top level rule: ->duplicateRef<-.
For further details see: https://sap.github.io/chevrotain/docs/FAQ.html#NUMERICAL_SUFFIXES