Placeholder label display setting has no front-end required indicator

Problem/Motivation

Given there is no label, there is no required marker, even though the field is set to mark required.

Steps to reproduce

1. Add a Name field to a content type and mark the field as required.
2. Manage field → open the settings:
   • Turn on Show component required marker (if you care about “(Required)” in placeholder).
   • Turn on Flags inputs as required (this is what the patch wires up for placeholder/none).
3. Set at least one text component’s Title display to placeholder (and optionally one to hidden/none).
4. Open Create node form:
   • Inspect the inputs: you should see the required attribute (and browser validation) when Flags inputs as required is on, after the patch.
   • With the marker setting on, placeholder text should still include (Required) where applicable.

Proposed resolution

Add `required="required"` to the sub fields

Remaining tasks

User interface changes

Before

After

API changes

Data model changes