SparkSQL: Create Table Delta Lake Variant

[R7L208]

Brief summary of the change made

Adds additional segments to support Delta Lake CREATE TABLE syntax

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

Additional sub-directory in test/fixtures/dialects/sparksql for delta related tests. It contains an README and test cases for Delta syntax. I thought this would be easier for troubleshooting and if Delta is ever split into it's own dialect.

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 #2954 (b7f0aa2) into main (b40eddf) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main     #2954   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          164       164           
  Lines        11852     11855    +3     
=========================================
+ Hits         11852     11855    +3     

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

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[tunetheweb]

The SQL file was not parsed into YAML since it was in a subdirectory. I suggest removing using a naming convention instead of a subfolder:

test/fixtures/dialects/sparksql/delta_create_table.sql

[tunetheweb]

One minor nit which I'll commit now.