Exasol: Improve COMMENT and WITH [NO] DATA clause usage.

[sti0]

Brief summary of the change made

This solves #2501. The COMMENT clause could now be used within CREATE TABLE AS SELECT... or CREATE VIEW statements without the need to force the SELECT statement within parentheses. Addionally this solves another TODO which forced the SELECT statement to be within parentheses when using the WITH [NO] DATA clause in CREATE TABLE AS SELECT statements.

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

Nope

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:

  • .yml rule test cases in test/fixtures/rules/std_rule_cases.
  • .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).
  • Full autofix test cases in test/fixtures/linter/autofix.
  • Other.

• Added appropriate documentation for the change.

• Created GitHub issues for any relevant followup/future enhancements if appropriate.

[codecov]

Codecov Report

Merging #2583 (3ae198c) into main (e1d4ec9) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main     #2583   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          163       163           
  Lines        11852     11861    +9     
=========================================
+ Hits         11852     11861    +9     

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

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