Issue #3450198 by jwilson3: Avoid clobbering existing field prefix, descriptions, and label suffix values

• Introduced helper functions to streamline message placement logic:
  • _label_help_append_title()
  • _label_help_append_label_suffix()
  • _label_help_prepend_description()
  • _label_help_prepend_field_prefix()
• Updated label_help_form_alter to use the new helper functions for:
  • Appending messages to element titles
  • Appending messages to label suffixes
  • Prepending messages to descriptions
  • Prepending messages to field prefixes
• This refactor enhances code readability and maintainability by reducing redundancy and centralizing the message attachment logic.

Closes #3450198