Snowflake: Add support for column rename

[wong-codaio]

Brief summary of the change made

Snowflake: Add support for column rename

fixes #2206

• Parsing errors for snowflake syntax #2206 has 2 issues. The first issue (SELECT TOP 1 *) has been fixed in Snowflake: Support TOP N select clause modifier #2222, and this PR should fix the second issue.
• This is part 2 of the overall plan to get tableColumnAction implemented Snowflake, as defined in Parsing errors for snowflake syntax #2206 (comment).

Are there any other side effects of this change that we should be aware of?

• None that I can think of.

Pull Request checklist

• Please confirm you have completed any of the necessary steps below.

• Included test cases to demonstrate any code changes, which may be one or more of the following:

  • .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).

[wong-codaio]

@tunetheweb @jpy-git - FYI - The 2nd step in the plan to get Snowflake's ALTER TABLE tableColumnAction implemented per #2206 (comment).

[codecov]

Codecov Report

Merging #2327 (a7328f6) into main (0ea874b) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main     #2327   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          159       159           
  Lines        11295     11295           
=========================================
  Hits         11295     11295           

Impacted Files	Coverage Δ
src/sqlfluff/dialects/dialect_snowflake.py	100.00% <ø> (ø)

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[jpy-git]

@wong-codaio nice work, looks great! LGTM 🚀 ✨