Add `dataDependencies.entityFields` to `JavaScriptComponent` config schema

Problem/Motivation

Currently, JavaScriptComponent config entities can declare data dependencies via dataDependencies.urls (external URLs fetched by the component) and dataDependencies.drupalSettings (Canvas Drupal settings needed by the component). However, there is no way for a JS component to declare that one of its props depends on entity field data.

This is the first foundational step toward #3573831: [META] Code Components: add an "entity reference" prop type — enables "view modes" that combine multiple entities plus static inputs!. Before the UI, runtime evaluation, or entity reference prop type can be built, the config schema needs to support declaring which entity fields each prop depends on.

Proposed resolution

Add a new optional entityFields key to the dataDependencies mapping on JavaScriptComponent config entities (canvas.js_component.*).

Schema structure:

• entityFields is optional (requiredKey: false), a sequence ordered by key
• Each key is a prop name from the component's props (validated via SequenceKeysMustMatch in subset mode)
• Each value is an array of field prop expression strings, validated by ValidStructuredDataPropExpression with allowed types:
  • FieldPropExpression
  • FieldObjectPropsExpression
  • ReferenceFieldPropExpression

Validation constraints:

• SequenceKeysMustMatch (extended): gained a matchType parameter with values same-set (default, pre-existing behavior — validated sequence must contain exactly the same keys as the target sequence) and subset (new — validated sequence's keys must all exist in the target sequence, but missing keys are allowed). Used here in subset mode so entityFields keys must be a subset of the component's props — only entity-reference props will have entityFields entries. Preferred over introducing a separate SequenceKeysAreSubsetOf constraint to avoid duplicating the sequence-comparison logic.
• EntityFieldExpressionsSameTarget (new): ensures all expressions within a single prop target the same entity type and bundle.
• ExpressionTargetEntityBundleExists (new): validates entity type existence and bundle existence for each expression string. (Originally scoped as ValidEntityFieldExpressionTarget; renamed for clarity — the constraint is reusable beyond the entityFields context.)
• Entity reference props cannot be required: props with entityFields entries must not appear in required (validated in JsComponentHasValidAndSupportedSdcMetadata). A referenced entity may disappear, so the component must tolerate NULL.

Config dependency calculation:

Override JavaScriptComponent::calculateDependencies() so each expression in dataDependencies.entityFields contributes its module and config dependencies (field configs, bundle configs, entity type provider modules) to the saved config entity. Follows the same addDependencies() pattern already used by ContentTemplate, Pattern, and PageRegion for component-tree expressions. Without this, ConfigDependencyManager would not know about the field/bundle/module references, breaking cascading deletes, import ordering, and cache invalidation.

OpenAPI:
The CodeComponent schema in openapi.yml is updated to document entityFields as an object with additionalProperties of type array<string>.

Remaining tasks

Review and commit.

User interface changes

None.

API changes

The dataDependencies object in API responses for code components (GET /canvas/api/v0/config/js_component/*) may now include an entityFields key. This is a backwards-compatible addition — existing responses without entityFields remain valid.

Data model changes

New optional key in canvas.js_component.* config schema:

dataDependencies:
  mapping:
    entityFields:
      requiredKey: false
      type: sequence
      orderby: key
      constraints:
        NotBlank:
          message: "There must be >=1 entity reference prop; otherwise the 'entityFields' key should be omitted."
        SequenceKeysMustMatch:
          matchType: subset
          propertyPathToSequence: props
      sequence:
        type: sequence
        orderby: value
        constraints:
          NotBlank:
            message: 'There must be >=1 entity field expression; otherwise the entity reference prop should be deleted.'
          EntityFieldExpressionsSameTarget: ~
        sequence:
          type: string
          constraints:
            ValidStructuredDataPropExpression:
              choices:
                - FieldPropExpression
                - FieldObjectPropsExpression
                - ReferenceFieldPropExpression
            ExpressionTargetEntityBundleExists: ~

No database changes. No config migration needed (requiredKey: false means existing JS components pass validation without changes).

The dependencies array on canvas.js_component.* exports may now include new module/config entries derived from entityFields.

Deferred to follow-ups

• Filter SequenceKeysMustMatch (in subset mode) to only entity reference props, rather than all props — requires the entity reference prop type from #3573831: [META] Code Components: add an "entity reference" prop type — enables "view modes" that combine multiple entities plus static inputs!.
• x-allowed-bundle validation for bundled entity types (e.g., require entity:node:article instead of entity:node) — also requires the entity reference prop type. Test coverage exists as a skipped test.