Allow per-function filtering of request telemetry

Today we log all results with the category `Host.Results`. Can we change that to be `Host.Results.`? Even if it requires a separate flag to enable (which it may not; I'm not thinking about this as breaking), it would open up a bunch of scenarios that in-proc customers currently rely on `ITelemetryProcessor`s to handle today. These aren't loaded by the host for out-of-proc scenarios.

No files or tests are named. Start by tracing where the host emits results under the Host.Results category and review how telemetry is handled for out-of-proc scenarios. Done means results can use a Host.Results. category and support per-function filtering, with any compatibility flag accounted for.

Written by the indexing model from the issue text.