Add parameter to make subset of AnyNumberOf() or AnySetOf() elements required

[chwiese]

There can be situations where statement parameters can be in arbitrary order, but they are still required. One example would be Snowflakes CREATE EXTERNAL TABLE statement, where LOCATION and FILE_FORMAT are required, but can be in arbitrary order with the other parameters, which are optional.

A parameter to make an element in a AnyNumberOf() or AnySetOf() required would address these situations. See #2421 for reference.