Central hub plugin. Implements ExtensiblePlugin to discover and wire all analytics extensions at startup.

1. During loadExtensions, discovers all QueryPlanExecutorPlugin, AnalyticsBackEndPlugin, and AnalyticsFrontEndPlugin implementations from extending plugins.
2. Creates the SchemaProvider (via OpenSearchSchemaBuilder, which converts OpenSearch ClusterState index mappings into a Calcite SchemaPlus).
3. Calls QueryPlanExecutorPlugin.createExecutor(backEnds) to build the QueryPlanExecutor.
4. Binds QueryPlanExecutor and SchemaProvider into Guice via lazy providers, so front-end transport actions can @Inject them.

This is the stable plugin name that all extending plugins declare in extendedPlugins. It owns no query language logic and no execution logic — it just discovers, wires, and exposes the components that other plugins provide.

• AnalyticsPlugin — The ExtensiblePlugin hub. Handles discovery, wiring, and Guice binding.
• OpenSearchSchemaBuilder — Converts ClusterState index mappings into Calcite tables with typed columns.