Unify Configuration and Initialization

[pellared]

Why

This is a "clone" of open-telemetry/opentelemetry-go#536 so that we can track adherence to https://github.com/open-telemetry/opentelemetry-go/blob/main/CONTRIBUTING.md#configuration

What

Modules compliance table:

Module	Compliant	Review date
.	✔️	2021-07-06
./detectors/aws	✔️	2021-07-06
./detectors/aws/ecs	✔️	2021-07-06
./detectors/aws/eks	✔️	2021-07-06
./detectors/gcp	✔️	2021-07-06
./exporters/metric/cortex	❌ ❓	2021-07-06
./exporters/metric/cortex/utils	❌ ❓	2021-07-06
./exporters/metric/datadog	❌ ❓	2021-07-06
./exporters/metric/dogstatsd	❌ ❓	2021-07-06
./instrumentation/github.com/Shopify/sarama/otelsarama	❌ #852 ⌛	2021-07-06
./instrumentation/github.com/astaxie/beego/otelbeego	❌ #853 ⌛	2021-07-06
./instrumentation/github.com/aws/aws-sdk-go-v2/otelaws	❌ #854 ⌛	2021-07-06
./instrumentation/github.com/bradfitz/gomemcache/memcache/otelmemcache	❌ #855 ⌛	2021-07-06
./instrumentation/github.com/emicklei/go-restful/otelrestful	❌ #856 ⌛	2021-07-06
./instrumentation/github.com/gin-gonic/gin/otelgin	❌ #857 ⌛	2021-07-06
./instrumentation/github.com/go-kit/kit/otelkit	❌ #858 ⌛	2021-07-06
./instrumentation/github.com/gocql/gocql/otelgocql	❌ #859 ⌛	2021-07-06
./instrumentation/github.com/gorilla/mux/otelmux	❌ #860 ⌛	2021-07-06
./instrumentation/github.com/labstack/echo/otelecho	❌ #861 ⌛	2021-07-06
./instrumentation/go.mongodb.org/mongo-driver/mongo/otelmongo	❌ #862 ⌛	2021-07-06
./instrumentation/google.golang.org/grpc/otelgrpc	❌ #863 ⌛	2021-07-06
./instrumentation/gopkg.in/macaron.v1/otelmacaron	❌ #864 ⌛	2021-07-06
./instrumentation/host	❌ #865 ⌛	2021-07-06
./instrumentation/net/http/httptrace/otelhttptrace	❌ #866 ⌛	2021-07-06
./instrumentation/net/http/otelhttp	❌ #750 #869 ⌛	2021-07-08
./instrumentation/runtime	❌ #867 ⌛	2021-07-06
./propagators	⚠️ ❌ #868 ⌛	2021-07-06
./propagators/aws	✔️	2021-07-06
./propagators/opencensus	✔️	2021-07-06
./tools	✔️	2021-07-06

[pellared]

@ercl Do you want to take over the exporters/metric/cortex part?

[pellared]

Is there anyone who wants to take care of exporters/metric/datadog and exporters/metric/dogstatsd?

[pellared]

During the SIG meeting, we agreed that we should also create a module for each propagator package.

[lastchiliarch]

Is there anyone who wants to take care of exporters/metric/datadog and exporters/metric/dogstatsd?

I'd like to have a try.