Provide asset metadata refresh/sync command

Problem/Motivation

When new metadata field mappings are added to an existing Acquia DAM media type (via the field map UI on /admin/structure/media/manage/{media_type}, the new mapping only takes effect for media entities created after the mapping was configured. Existing media entities are never updated, their newly-mapped fields remain empty (or hold stale values).

The existing sync mechanisms don't cover this:

• Cron sync (acquia_dam_cron → syncAssets()) only processes media whose DAM assets were recently edited (based on lastEditDate). Unedited assets are skipped.
• Manual "Sync metadata" action works per-entity only — no batch operation exists.
• acquia-dam:update-assets is DAM-API-centric (version checks, queue processing) and isn't designed for re-applying field configurations locally.

There is no way for a site administrator to retroactively apply field mapping changes to thousands of existing media entities without manually editing each one or resorting to custom update hooks.

Steps to reproduce

• Update field map at /admin/structure/media/manage/{media_type}
• Newly mapped fields are empty for existing assets.

Proposed resolution

Add a new Drush command acquia-dam:asset-sync-metadata (ad:asm) that iterates all existing DAM media entities of a given media type and force-refreshes their mapped metadata fields.

The command:

• Accepts a required media_type argument — only processes media of that type, preventing accidental bulk operations.
• Uses forceMappedFieldRefresh() logic (same as the "Sync metadata" UI action and the MediaItemUpdater cron worker) to unconditionally overwrite all mapped fields with current values from getMetadata(), including entity_reference resolution to taxonomy terms.
• Processes in configurable batches (--batch-size, default 50) with entity cache clearing and periodic garbage collection to handle large media inventories.
• Supports resumable processing (--resume flag) — stores the last processed media ID in Drupal state (acquia_dam.metadata_sync.last_processed_id) after each chunk. If interrupted (timeout, crash), re-running with --resume picks up where it left off rather than starting over.
• Validates the media type argument via a Drush hook validator — only media types using the acquia_dam_asset source plugin are accepted, with a helpful error listing available types.

Usage examples:

drush adsmm acquia_dam_image_asset
drush adsmm acquia_dam_pdf_asset --batch-size=100 --resume