Add Case property to FormatConfig

[asherber]

My team prefers lowercasing sql reserved words.

This PR replaces the boolean Uppercase property with a CaseTypes enum supporting NONE, UPPER, and LOWER. The formatter's Show() method is updated to apply .ToLower() or .ToUpper() based on the enum value.

The previous bool uppercase constructor and Uppercase(bool) builder method are preserved but marked [Obsolete], delegating to the new CaseTypes-based path. The Uppercase property is similarly obsoleted but kept for backwards compatibility, deriving its value from Case == CaseTypes.UPPER.

Tests cover all three CaseTypes values for both formatting behavior and the legacy Uppercase property.

[hogimn]

Thank you for the great PR! I really appreciate how you handled the backward compatibility with [Obsolete] while introducing the new CaseTypes enum.

[asherber]

Thanks for accepting, and sorry about the several style violations.

[hogimn]

No problem at all. Thank you for contributing. (＾▽＾)