Grammar: Tidy up Snowflake/MySQL/HIVE USE statements

[jpy-git]

Brief summary of the change made

The Snowflake USE statement was missing USE SECONDARY ROLES grammar. Also it had previously been moved to ANSI in #950 but this doesn't make sense as other dialects (hive and mysql) only have USE <database> so cleaned this up.

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

No

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 #2187 (889d783) into main (e5d9a85) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main     #2187   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          148       148           
  Lines        10778     10777    -1     
=========================================
- Hits         10778     10777    -1     

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

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