MLHR-866 Annotating Stateless operators

Annotating stateless operators.

For some stateless operators, comments was mentioning the operator does not maintain any state, (First, MatchTill operators are using a boolean as a state), correcting that too

FirstMatchMap             (emitted is a state)
FirstMatchStringMap    (emitted is a state)
FirstTillMatch               (emitted is a state)
FirstTillMatchString     (emitted is a state)
InsertionSort               (AbstractBaseSortOperator has pqueue and pmap as a state).