Refactor tag access patterns to use a centralized caching mechanism with embedded type default behavior.

Centralized tag management with caching and embedded type handling.

For anonymous/embedded fields (fields with no names):

• Default (empty string): Treated as regular fields (requires explicit tstype:",extends" tag)
• Configurable: Set embedded_field_behavior with tag-like syntax
• Syntax: Uses tag-like syntax, e.g., "extends,required"
• Examples:
  • "" - Treat as regular field
  • "extends" - Extends, optional (wrapped in Partial<>)
  • "extends,required" - Extends and required
• Override: Explicit tstype:"-" or tstype:",extends" tags always respected