Change default prometheus host from 0.0.0.0 to localhost

[jack-berg]

Prometheus spec for both the env var and programmatic config says the default host should be localhost:

• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md#host
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#prometheus-exporter

(This is the result of a change from 2022: ttps://github.com/open-telemetry/opentelemetry-specification/pull/2282)

In java, we default to 0.0.0.0:

We should update to align with spec.

This is breaking change, but is allowed since PrometheusHttpServer is experimental. Unfortunately, I don't think there's a great way to make this change without ripping the bandaid off. Maybe we could detect that the default host was used, and log a warning indicating that the default has changed.