Implement generic way to include relevant policy settings at http context

[sjberman]

Right now we have generic policy logic that will include all policy configuration at the server or location context (where the policy is attached). However, some policies (like the ObservabilityPolicy) may have settings that need to live at the http context. Right now there is specialized logic when building the telemetry configuration (in the http context) that includes the settings from the ObservabilityPolicy.

We should figure out a way to make this logic more generic so that any policy that has configuration at the http context can easily include it there without the need for the dataplane configuration builder to know about it.