Snowflake: support for extended column options in CREATE TABLE

[7phs]

Snowflake supports several extended options for column definitions:

-- Column definition
    <col_name> <col_type>
      [ inlineConstraint ]
      [ NOT NULL ]
      [ COLLATE '<collation_specification>' ]
      [
        {
          DEFAULT <expr>
          | { AUTOINCREMENT | IDENTITY }
            [
              {
                ( <start_num> , <step_num> )
                | START <num> INCREMENT <num>
              }
            ]
            [ { ORDER | NOORDER } ]
        }
      ]
      [ [ WITH ] MASKING POLICY <policy_name> [ USING ( <col_name> , <cond_col1> , ... ) ] ]
      [ [ WITH ] PROJECTION POLICY <policy_name> ]
      [ [ WITH ] TAG ( <tag_name> = '<tag_value>' [ , <tag_name> = '<tag_value>' , ... ] ) ]
      [ COMMENT '<string_literal>' ]

This merge request implements support for these additional column options.