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

See forge#99699

Description 

TCA type link fields now support editing and persisting the rel attribute in the normal link browser.

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.