Snowflake: Support dollar quoted comments

[7phs]

Snowflake supports dollar-quoted comments as string literals when creating tables, views, and their fields.

For example:

CREATE OR REPLACE TEMPORARY VIEW foo.bar.baz (
    "COL_1" COMMENT $$comment 1$$
) COMMENT = $$view comment$$ AS (
    SELECT 1
)

This pull request adds support for this type of comments.

[iffyio]

LGTM! Thanks @7phs!
cc @alamb

[alamb]

🚀