Feature: #99699 - Enable rel attribute for link fields outside of the RTE 

Description 

TCA type link fields now support editing and persisting the rel attribute in the regular link browser as well.

When appearance.allowedOptions contains rel, the link browser renders a dedicated relationship input field for non-RTE link fields (for example tt_content.header_link).

The TypoLink codec supports an optional sixth TypoLink segment for rel, and frontend TypoLink rendering now applies this value to generated anchor tags.

Impact 

Integrators can now use rel consistently in link browser dialogs for both RTE and non-RTE link fields.

Existing TypoLink values without rel remain unchanged and continue to work as before.