pyroscope.receive_http treats headers inconsistently

[simonswine]

pyroscope.receive_http supports forwarding pushv1 and ingest handler.

For the pushv1 non of the headers are forwarded, while the ingest handler forwards all but a block list of headers:

https://github.com/simonswine/alloy/blob/755bcfcb5ab193488a226f467216b93ce98c6cd1/internal/component/pyroscope/write/write.go#L45-L52

I suggest we should only forward headers, that are important for parsing of the profiles, which includes:

• Content-Type