entity_form_field_label 3.x-dev

First pre-release of the 3.x branch. Significant architectural rework
under issue #3591474.

WHAT'S NEW

- New FieldFormAlterer plugin type: per-field-type rewriting logic
lives in dedicated, attribute-discoverable plugin classes
(Plugin/FieldFormAlterer/*). Other modules can contribute their own.
- Plugins declare weight (execution order) and exclusive (whether
they terminate the chain on match — lowest weight wins among matches).
- Four built-in plugins: entity_reference, color_field, composite
("||"-separated values), simple (catch-all).
- Field description (help text) can now be rewritten on widgets, in
addition to the label — including composite "||" support.
- New kernel test suite covering weight/exclusive semantics and
description handling.

BREAKING CHANGES

- Drupal 11+ only. Drupal 9 and 10 are no longer supported on this
branch; use 2.x for those.
- All _entity_form_field_label_* procedural helpers have been removed
in favour of the plugin system. If you previously extended via those
helpers, see the README for the new extension point.

CONFIGURATION COMPATIBILITY

The third-party settings keys (rewrite_label, new_label) and the
existing config schema are unchanged. Form/view display entities
upgraded from 2.x keep working without intervention. The new keys
(rewrite_description, new_description) are optional.

UPGRADING FROM 2.x

1. Bump core to ^11 if you haven't already.
2. Replace dev-2.x / ~2.0 in your composer constraint with ^3.0@alpha.
3. Run `drush updb` (no DB updates are required at this time but it's
good practice).
4. If you had custom code calling _entity_form_field_label_* functions,
port it to a FieldFormAlterer plugin (see the README example).

KNOWN LIMITATIONS

- API may still change before the stable 3.0.0 release based on
community feedback. Pin to an exact alpha if you ship to production.
- Description rewriting applies to widgets only (form display); view
displays already render labels but not field help text.

Reviews welcome on issue #3591474.