CREATE VIEW multiple column options and Snowflake fixes

[eliaperantoni]

A Snowflake query like:

CREATE VIEW X (COL WITH TAG (pii='email') COMMENT 'foobar') AS SELECT * FROM Y

Would've previously failed because of two reasons:

• It contains two options for the COL column, but only one is currently parsed for CREATE VIEW statements.
• It uses an option other than COMMENT, which is the only one currently supported for the Snowflake dialect.

This PR fixes both.

Additionally, it records in the AST whether the options are comma separated or not. Otherwise, ToString wouldn't produce a syntactically valid query for Snowflake.