Support configurable list of metadata_keys that can be used to set client address

[isaacaflores2]

Component(s)

No response

Is your feature request related to a problem? Please describe.

Currently both confighttp and configgrpc set the client address based only one value RemoteAddress or peer address respectively

1. confighttp: https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/confighttp/clientinfohandler.go#L34
2. configgrpc: https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/configgrpc/configgrpc.go#L591

In some cases the clients may not set RemoteAddress or peer or a specific environment may require deriving the client address from other request information.

Describe the solution you'd like

Expose a list of metdata_keys (headers) that can be used to determine the client address.
The first valid key value can be used to set the client.Address. An example would be checking the following keys in order: x-forwarded-for, x-real-ip and using the first valid ip.

Describe alternatives you've considered

No response

Additional context

No response

Tip

_{React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it. Learn more here.}