Describe the enhancement:
Add OTel Collector Contrib headerssetterextension to EDOT

Describe a specific use case for the enhancement or feature:
The headers_setter extension implements ClientAuthenticator and is used to set requests headers in gRPC / HTTP exporters with values provided via extension configurations or requests metadata (context).
Use cases include but are not limited to enabling multi-tenancy/routing for observability backends.

What is the definition of done?
The extension can be used in EDOT configuration to add customer headers to gRPC / HTTP OTel exporters requests.