SDC `enum` props should have translatable labels: use `meta:enum`

Problem/Motivation

Enum vales do not have (translatable) labels.

We need human-readable equivalents, and those equivalents must be translatable (using Drupal's interface translation mechanism).

Precedent:

• Core: #3471494: Add an icon management API
• The https://www.drupal.org/project/ui_patterns contrib module: \Drupal\ui_patterns\EnumTrait::getEnumOptions()

Steps to reproduce

The core/modules/system/tests/modules/sdc_test/components/my-banner/my-banner.component.yml SDC contains:

    ctaTarget:
      title: CTA Target
      type: string
      enum:
        - ''
        - _blank

👆 Clearly the supported '' enum value is impossible to generate a sensible human-readable label for.

Proposed resolution

Change that example to:

    ctaTarget:
      title: CTA Target
      type: string
      enum:
        - ''
        - _blank
      meta:enum:
        '': 'Same window'
        _blank: 'Open in new window'

… and which if accessed through some TBD API should be passed through Drupal's UI translation mechanism, like so:

\Drupal\Core\StringTranslation\StringTranslationTrait::t(
  string: 'Same window,
  options: ['context' => 'sdc_test:my_banner, ctaTarget prop'],
)

Which would then result in Hetzelfde venster in Dutch (nl) or Même fenêtre in French (fr).

Remaining tasks

1. INFRA: Update \Drupal\Core\Theme\Component\ComponentMetadata::parseSchemaInfo() to trigger a deprecation error when an enum is encountered without a corresponding meta:enum
2. INFRA: Update \Drupal\Core\Theme\Component\ComponentMetadata::parseSchemaInfo() to trigger a \LogicException when a meta:enum is encountered whose keys do not match (i.e. are a subset or superset) the values listed in the corresponding enum.
3. Compliance: Update sdc_test:my-banner like the above. Update all other core SDCs to provide a meta:enum. (The first 2 tasks will guarantee this.)
4. INFRA: add a getEnumOptions(string $prop): array<string, TranslatableMarkup> method to \Drupal\Core\Theme\Component\ComponentMetadata inspired by ui_patterns'\Drupal\ui_patterns\EnumTrait::getEnumOptions(). (The thing that ui_patterns does not yet do is pass it through Drupal's t().)
5. TEST: kernel test asserting that 2 identical type: string, enum: […] props can have different translations for the same enum values. For example: a '' enum value results in Same window for the target prop and in None for a rel prop.
   → verifies it works end-to-end, and supports translation contexts
6. TEST: expand the previous point's test to test at least one language other than English.
7. TEST: kernel test asserting that a meta:enum not matching the enum triggers a \LogicException

User interface changes

None.

Introduced terminology

None.

API changes

1. Every enum SDC prop now supports a meta: enum, will be required in Drupal 12.
2. Every enum SDC prop that has a meta: enum requires them to be in sync, otherwise an exception is thrown.

Data model changes

None.

Release notes snippet

Single-Directory Components with props that have a restricted set of allowed values (using enum) now can specify human-readable labels for each of those allowed values. Those labels are also translatable using Drupal's user interface translation subsystem, and they have an SDC prop-specific context (<provider>:<sdc_name>, <prop name> prop).