This stops invoking Telemetry::sync() via a scheduled event and instead
only invokes it on-demand. This makes metric collection network time
independent and lazier, too.
With Prometheus scrape requests being processed on Zeek's main thread
now, we can safely invoke the script layer Telemetry::sync() hook.
Closes#3947
With Cluster::Node$metrics_port being optional, there's not really
a need for the extra script. New rule, if a metrics_port is set, the
node will attempt to listen on it.
Users can still redef Telemetry::metrics_port *after*
base/frameworks/telemetry was loaded to change the port defined
in cluster-layout.zeek.
Adds base/frameworks/telemetry with wrappers around telemetry.bif
and updates telemetry/Manager to support collecting metrics from
script land.
Add policy/frameworks/telemetry/log for logging of metrics data
into a new telemetry.log and telemetry_histogram.log and add into
local.zeek by default.
