feat(fieldset): fieldset message must be ids-hint-message element

[laszloilonka]

IDS-2503

Breaking change: idsFieldsetMessage restricted to ids-hint-message

idsFieldsetMessage can no longer be applied to arbitrary elements. It must be used on an ids-hint-message component.
The IdsFieldsetMessageDirective selector changed from [idsFieldsetMessage] to ids-hint-message[idsFieldsetMessage]. Only ids-hint-message elements with the idsFieldsetMessage attribute are projected into the fieldset message area.

Migration

Before:

<div idsFieldsetMessage>Helper text</div>

After:

<ids-hint-message idsFieldsetMessage>
  Helper text
</ids-hint-message>

If you were already using ids-hint-message with idsFieldsetMessage, no changes are required.

Notes

• Fieldset-level messages now use the same hint message styling and behavior as form-field messages.
• Nested ids-hint-message elements inside ids-form-field are unaffected.