Caught by:
go test -race ./internal/cmd/pomerium
The ctx in Run is both read (in handle signal goroutine) and write
(when passing to errgroup context in Run), causes data race.
Fixing it, by passing the ctx to goroutine via argument instead of
accessing it directly.
- Update envoy bootstrap config to protobufs
- Reorganize tracing config to avoid cyclic import
- Push down zipkin config to Envoy
- Update tracing options to provide sample rate
