SQLite: Support CAST(expr AS) without a type name

[LucaCappelletti94]

This PR lets SQLiteDialect parse a CAST whose type name is empty, which SQLite accepts, and round-trips it unchanged.

SELECT CAST(a AS);
-- Previously: Expected: a data type name, found: )

The type name in SQLite's CAST grammar may be empty.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.11%. Comparing base (bfc7d38) to head (ac49b34).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2558      +/-   ##
==========================================
+ Coverage   81.09%   81.11%   +0.01%     
==========================================
  Files          42       42              
  Lines       33682    33691       +9     
  Branches    33682    33691       +9     
==========================================
+ Hits        27316    27327      +11     
  Misses       2796     2796              
+ Partials     3570     3568       -2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.