Add exporter_creator component

[stuart23]

Description

This PR adds the exporter_creator component that dynamically creates exporters at runtime based on observed endpoints from observer extensions (such as k8s_observer and jsonfile_observer). The component enables dynamic telemetry routing based on resource attributes, allowing exporters to be created and configured automatically when Kubernetes CRDs or other infrastructure resources are discovered.

Key features:

• Dynamic exporter creation based on observer endpoint discovery
• Telemetry routing based on resource attribute matching
• Support for k8s CRD and JSON file observers
• Metrics for tracking created exporters and non-routable telemetry
• Configuration expansion using endpoint properties

Link to tracking issue

Fixes #45801

Testing

• Added comprehensive unit tests for routing logic (router_test.go, router_mismatch_test.go)
• Added tests for config expansion (config_expansion_test.go)
• Added tests for CRD observer routing (crd_test.go, observer_routing_test.go)
• Added tests for wrapped exporter functionality (exporter_wrapped_test.go)
• All tests pass and provide coverage for:
  • Resource attribute to endpoint property matching
  • Configuration expansion with backtick expressions
  • Dynamic exporter creation and lifecycle management
  • Telemetry routing to matched exporters
  • Handling of non-routable telemetry

Documentation

• Added README.md with component overview, configuration examples, and usage instructions
• Added documentation for routing rules and exporter templates
• Added examples for endpoint value expansion
• Component is marked as [development] stability for logs, metrics, and traces