[jaeger-v2] Document changes to admin port / services

[yurishkuro]

• metrics are on a different port address: 0.0.0.0:8888 (address: 0.0.0.0:8889 for ingester)
• expvar is also on a different port via expvar extension: port: 27777
• Healthchecks are on a different port via healthcheckv2 extension: endpoint: "0.0.0.0:13133"

[jkowall]

I did some updates to the docs per : #751

The following seem to still be in the v1 docs and I believe should be somewhere in v2 docs, let me know what you think:

At default settings **jaeger-collector** exposes the following ports:

| Port  | Protocol | Endpoint | Function
| ----- | -------  | -------- | ----
| 4317  | gRPC     | n/a      | Accepts traces in [OpenTelemetry OTLP format][otlp] (Protobuf).
| 4318  | HTTP     | `/v1/traces` | Accepts traces in [OpenTelemetry OTLP format][otlp] (Protobuf and JSON).
| 14268 | HTTP     | `/api/sampling` | Serves sampling policies (see [Remote Sampling](../sampling/#remote-sampling)).
|       |          | `/api/traces` | Accepts spans in [jaeger.thrift][jaeger-thrift] format with `binary` thrift protocol (`POST`).
| 9411  | HTTP     | `/api/v1/spans` and `/api/v2/spans` | Accepts Zipkin spans in Thrift, JSON and Proto (disabled by default).
| 14250 | gRPC     | n/a      | Used by **jaeger-agent** to send spans in [model.proto][] Protobuf format.

[yurishkuro]

yes, those ports would still be relevant (sometimes the ports might be different)