feat(otlp): experimental otlp support

[petethepig]

• very much a draft at this point.
• requires a copy of https://github.com/open-telemetry/opentelemetry-proto-profile to be adjacent to the directory
• works with https://github.com/grafana/pyroscope/pull/2177 and https://github.com/petethepig/opentelemetry-collector/pull/1

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[korniltsev]

May be a good idea to make Remote an interface and otlp implementation of that interface and maybe put otlp implementation in to a separate module, so that people who don't need grpc dependencies do not get them accidentally