Create example Alerts for when a Gateway or HTTPRoute is not protected by Kuadrant Polices

[david-martin]

These will be based on the absence of specific Policies targeting a HTTPRoute or Gateway.

• Alert if a Gateway does not have a DNSPolicy targeting it
• Alert if a Gateway does not have a TLSPolicy targeting it
• Alert if a HTTPRoute does not have an AuthPolicy targeting it
• Alert if a HTTPRoute does not have a RateLimitPolicy targeting it

These alerts will need to depend on metrics exported by https://github.com/Kuadrant/gateway-api-state-metrics/tree/main

Changes may be needed to expose the relationship (targetRef) information as state metrics so that the alert query can be written

[david-martin]

example alert query

label_replace(gatewayapi_gateway_info, "gateway_name", "$1", "name", "(.*)")

unless 

(label_replace(gatewayapi_gateway_info, "gateway_name", "$1", "name", "(.*)")
* on(gateway_name) group_left
label_replace(gatewayapi_dnspolicy_target_info{target_kind="Gateway"}, "gateway_name", "$1", "target_name", "(.*)"))