support Headers Setter extension

[sedlak7]

Hello Team

Please, could you add Headers Setter extention into collector.

https://github.com/open-telemetry/opentelemetry-collector-releases/blob/main/distributions/otelcol-k8s/manifest.yaml#L13
https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/extension/headerssetterextension/README.md

It will help with multi-tenancy for backends.

Thanks in advance
Peter

[andreasgerstmayr]

@sedlak7 which headers do you want to set?

The otlp and otlphttp exporter for example can set custom headers (see https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/confighttp/README.md#client-configuration).

Here's an example with multi-tenancy, setting the tenant in the header and auth token with the bearertokenauth extension: https://github.com/grafana/tempo-operator/blob/main/tests/e2e-openshift/multitenancy/02-install-otelcol.yaml#L25-L42