Add migration/pkg/catalogmigration: CatalogSource → ClusterCatalog (Phase 5)

Implements the catalog migration library (R8) that converts OLMv0
CatalogSources to OLMv1 ClusterCatalogs.

Key behaviors:
  - Scans all CatalogSources across all namespaces before creating any
    ClusterCatalogs to determine the naming strategy
  - Naming strategy (R8): same name + same image → consolidate; same
    name + different image → <name>-<namespace>; unique name → use as-is
  - Adopt-or-create: existing ClusterCatalog with matching image ref is
    adopted; idempotent migrated-from-catalogsource annotation
  - Poll interval converted only when explicitly set; digest refs get no
    poll interval
  - int32 priority range validated; --acknowledge-priority-overflow caps
    at MaxInt32/MinInt32
  - spec.secrets and spec.grpcPodConfig noted (no OLMv1 equivalent)
  - --delete-catalogsource requires both flag AND no referencing Subscriptions

API:
  CatalogMigrator.MigrateCatalogs(ctx, CatalogMigratorOptions) → results
  CatalogMigrationResult: status, reason, notes (informational)

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Todd Short <tshort@redhat.com>

Author: tmshort