Dedup command doesn't require the fieldList parameter

[51-code]

Describe the bug

For example, a query like:
| dedup consecutive=true _raw

will result in a parse tree that does not include the "_raw" field.

This has two reasons:

• The FieldList ("_raw" in this case) is not required, it is optional
• The optional parameters in dedup are required to be given on the right hand side of the FieldList, even though it should not matter

So, with the query above, the fieldList is not required, so it skips it completely and moves on to parsing the optional parameters ("consecutive") and then it will stop parsing because a fieldList is not expected anymore.

Expected behavior

The query should work.

How to reproduce

Run a query like this:
index=abc | dedup consecutive=true _raw

It actually throws a NullPointerException in PTH-10 because it always expects a FieldList and visits it even though it isn't there for this query.

Screenshots

Software version

6.1.0

Desktop (please complete the following information if relevant):

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Additional context

The grammar change may require changes in PTH-10 as well. For allowing parameters on each side of the FieldList, it probably has to be checked in PTH-10 that each of the parameters is only given once.

dedupConsecutiveOnLeftSideOfFieldListTest and dedupKeepemptyOnLeftSideOfFieldListTest in TicketSyntaxTests.java have been disabled because of this issue in PR #52.