Snowflake: support of views column comment

[7phs]

Snowflake supports adding comments to fields within a view:

CREATE OR REPLACE VIEW v (a COMMENT 'Comment of field') AS SELECT a FROM table1

This MR introduces support for this feature.

Additionally, I noticed that the view's comment was not in the correct order—this issue surfaced while testing with a large query from a Snowflake production environment. The comment for the view should appear after the column list. I've included this minor fix in this MR as well. Please let me know if you think it would be better to address this in a separate MR.

[coveralls]

Pull Request Test Coverage Report for Build 11101253622

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 27 of 29 (93.1%) changed or added relevant lines in 4 files are covered.
• 1219 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.03%) to 89.322%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ast/mod.rs	4	5	80.0%
tests/sqlparser_snowflake.rs	20	21	95.24%

Files with Coverage Reduction	New Missed Lines	%
src/parser/alter.rs	28	76.07%
src/ast/ddl.rs	64	86.67%
tests/sqlparser_common.rs	300	89.58%
src/ast/mod.rs	391	82.4%
src/parser/mod.rs	436	93.36%

Totals
Change from base Build 10980785660:	-0.03%
Covered Lines:	29948
Relevant Lines:	33528

---

💛 - Coveralls

[iffyio]

LGTM! cc @alamb

[alamb]

Thank you @7phs and @iffyio