Enhancement: Use secret for sumologic url in built in sumologic metrics handler

[jspaleta]

Talked with engineering. the built in sumologic metrics handler resource type does have support for url using env_var backed secrets.

So it should be possible to update the integration to use the same workflow as the slack integration's secret url. Here's an example I was given, but haven't tested yet.

type: SumoLogicMetricsHandler
api_version: pipeline/v1
metadata:
name: demo-sumo-handler
namespace: default
spec:
url: https://long-events.sumologic.net/receiver/v1/http/$SUMO_HTTP_KEY
secrets:
- name: SUMO_HTTP_KEY
secret: sumo_http_key
max_connections: 10
timeout: 30s