Integrate entity_mesh tracking with entity_registry consumer plugin system

Problem/Motivation

entity_mesh maintains its own tracking and indexation system (entity_mesh_tracker table, Tracker/TrackerManager classes, lifecycle hooks, and cron handler) for managing entity processing. This duplicates
functionality already provided by the entity_registry module's consumer plugin system, resulting in two parallel tracking implementations that must be maintained independently.

Proposed resolution

Create an EntityMeshConsumer plugin that implements EntityRegistryConsumerInterface, delegating all entity tracking, lifecycle detection, and cron processing to entity_registry.
The consumer wraps entity_mesh's existing rendering and link-extraction pipeline (EntityRender, Repository) while preserving sync/async processing modes and source/target type configuration.

• Add a new EntityMeshConsumer plugin class
• Remove entity_mesh's built-in lifecycle hooks, cron handler, and tracker classes
• Decouple Entity, EntityRender, and Menu classes from TrackerManager
• Add entity_registry as a module dependency
• Deprecate batch routes that relied on the removed tracker (to be replaced in a follow-up)

Remaining tasks

• Replace deprecated batch forms and routes with entity_registry equivalents
• Update Drush commands to use entity_registry's processor
• Remove the entity_mesh_tracker table via update hook once transition is verified
• Add unit tests for the consumer plugin

User interface changes

Entity Mesh appears as a registered consumer in the entity_registry admin UI at /admin/config/system/entity-registry, providing status counts, populate, reindex, clear, and rebuild
actions.

API changes

• Removed services: entity_mesh.tracker, entity_mesh.tracker_manager
• Removed classes: Tracker, TrackerInterface, TrackerManager, TrackerManagerInterface
• Changed constructor signatures: Entity, EntityRender, Menu no longer accept TrackerManagerInterface
• Removed hooks: hook_entity_insert, hook_entity_update, hook_entity_delete, hook_cron

Data model changes

No changes to the entity_mesh data table. The entity_mesh_tracker table is retained in schema but no longer actively used. Removal is planned for a future update hook.