feat: instrument grpc client with otel

[haoqixu]

What's changed and what's your intention?

This PR instruments the grpc client with otelgrpc and provides configurable settings for SDK telemetry.

Differences from #8

The main differences are:

• This PR uses opentelemetry SDK instead of prometheus SDK and collects not only metrics but also traces.
• This PR does not make decisions for users about observability strategy like metrics format, prometheus endpoint and metrics prefix/namespace. Users can provide their own MeterProvider/TracerProvider to decide their observability strategy and easily integrate the SDK telemetry into the application by reusing the providers.

If we already instrument our services with prometheus and want to integrate greptimedb-ingester-go, we can do it like:

package main

import (
	// ...

	otelprom "go.opentelemetry.io/otel/exporters/prometheus"
	"go.opentelemetry.io/otel/sdk/metric"

	// ...
)

func main() {
	// Register to the default global prometheus.Registerer.
	// We can also pass a prometheus.Registerer to otelprom.New(), or use exporter as prometheus.Collector
	exporter, err := otelprom.New(otelprom.WithNamespace("greptime"))
	if err != nil {
		log.Fatal(err)
	}
	meterProvider := metric.NewMeterProvider(
		metric.WithReader(exporter),
	)

	cfg := greptime.NewConfig("localhost").
		WithMetricsEnabled(true).  // enable it
		WithMeterProvider(meterProvider).  // custom provider, nil to use otel global meter provider
		WithDatabase("public")

	// ...
}

Maybe we can add the snippet to examples. 🤔

Checklist

• I have added the necessary unit tests and integration tests.

Refer to a related PR or issue link (optional)

Fixes #8

[daviderli614]

Thank for your contribution. Can you fix the CI error? @haoqixu
It seems that the new file not have a License header, and build errors.

[daviderli614]

LGTM