Use `hs-opentelemetry-api` in `eventlog-live-otelcol`

[wenkokke]

This requires:

• upstreaming the gRPC exporter to hs-opentelemetry-api
• adding metric support to hs-opentelemetry-api

[wenkokke]

The primary motivator for this is that OpenTelemetry has a complicated and evolving specification for configuration via environment variables and using hs-opentelemetry-api externalises and centralises the responsibility for supporting that specification. For details, see:
https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/

[wenkokke]

It's tricky to use hs-opentelemetry-api from eventlog-live-otelcol, because the former is designed from the ground up to be used to instrument code, e.g., to create a span from known data, you have to call createSpanWithoutCallStack followed by endSpan, and if Nothing is passed for either Maybe Timestamp argument or createSpan is used instead, then hs-opentelemetry-api will insert data from eventlog-live-otelcol rather than throwing an error or drawing data from the monitored process. This seems like a maintenance trap, where, because they're so difficult to spot, eventually such errors will sneak in.