This allows tracing the startup actions e.g. with Jaeger
(https://www.jaegertracing.io/). We use the "tracing-opentelemetry"
crate, which turns tracing spans into OpenTelemetry spans, so you can
use the usual "#[instrument]" directives to add tracing.
I put the tracing initialization code to a separate crate,
`tracing-utils`, so that we can reuse it in other programs. We
probably want to set up tracing in the same way in all our programs.
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
