Telemetry framework: move BIFs to the primary-bif stage

This moves the Telemetry framework's BIF-defined functionalit from the
secondary-BIFs stage to the primary one. That is, this functionality is now
available from the end of init-bare.zeek, not only after the end of
init-frameworks-and-bifs.zeek.

This allows us to use script-layer telemetry in our Zeek's own code that get
pulled in during init-frameworks-and-bifs.

This change splits up the BIF features into functions, constants, and types,
because that's the granularity most workable in Func.cc and NetVar. It also now
defines the Telemetry::MetricsType enum once, not redundantly in BIFs and script
layer.

Due to subtle load ordering issues between the telemetry and cluster frameworks
this pushes the redef stage of Telemetry::metrics_port and address into
base/frameworks/telemetry/options.zeek, which is loaded sufficiently late in
init-frameworks-and-bifs.zeek to sidestep those issues. (When not doing this,
the effect is that the redef in telemetry/main.zeek doesn't yet find the
cluster-provided values, and Zeek does not end up listening on these ports.)

The need to add basic Zeek headers in script_opt/ZAM/ZBody.cc as a side-effect
of this is curious, but looks harmless.

Also includes baseline updates for the usual btests and adds a few doc strings.

(cherry picked from commit 71f7e89974)

scripts/base/frameworks/telemetry/main.zeek

@@ -5,28 +5,10 @@
 ##! enabled by setting :zeek:see:`Telemetry::metrics_port`.
 
 @load base/misc/version
-@load base/frameworks/cluster
-
-@load base/frameworks/telemetry/options
+@load base/bif/telemetry_functions.bif
 
 module Telemetry;
 
-# In a cluster configuration, open the port number for metrics
-# from the cluster node configuration for exporting data to
-# Prometheus.
-#
-# The manager node will also provide a ``/services.json`` endpoint
-# for the HTTP Service Discovery system in Prometheus to use for
-# configuration. This endpoint will include information for all of
-# the other nodes in the cluster.
-@if ( Cluster::is_enabled() )
-redef Telemetry::metrics_endpoint_name = Cluster::node;
-
-@if ( Cluster::local_node_metrics_port() != 0/unknown )
-redef Telemetry::metrics_port = Cluster::local_node_metrics_port();
-@endif
-@endif
-
 export {
 	## Alias for a vector of label values.
 	type labels_vector: vector of string;

scripts/base/frameworks/telemetry/options.zeek

@@ -1,9 +1,10 @@
-module Telemetry;
+##! Configurable settings for the Telemetry framework.
+##!
+##! These reside separately from the main framework so that they can be loaded
+##! in bare mode without all of the framework. This allows things like the
+##! plugins.hooks test to see the options without needing the rest.
 
-# This file contains the options for the Telemetry framework. These are kept
-# separately so that they can be loaded in bare mode without loading all of
-# the rest of the framework. This allows things like the plugins.hooks test
-# to see the options without needing the rest.
+module Telemetry;
 
 export {
 	## Address used to make metric data available to Prometheus scrapers via
@@ -19,3 +20,23 @@ export {
 	## defaults to the name of the node in the cluster configuration.
 	const metrics_endpoint_name = "" &redef;
 }
+
+# When running a cluster, use the metrics port from the cluster node
+# configuration for exporting data to Prometheus.
+#
+# The manager node will also provide a ``/services.json`` endpoint
+# for the HTTP Service Discovery system in Prometheus to use for
+# configuration. This endpoint will include information for all of
+# the other nodes in the cluster.
+
+# We do this here, and not in main.zeek, to avoid ordering issues when loading
+# the telemetry and cluster frameworks. This applies even in bare mode, per
+# init-frameworks-and-bifs.zeek: the cluster's metrics ports need to be available
+# for the redefs to assign the correct values.
+@if ( Cluster::is_enabled() )
+redef Telemetry::metrics_endpoint_name = Cluster::node;
+
+@if ( Cluster::local_node_metrics_port() != 0/unknown )
+redef Telemetry::metrics_port = Cluster::local_node_metrics_port();
+@endif
+@endif

scripts/base/init-bare.zeek

@@ -5787,15 +5787,11 @@ export {
 	const flowbuffer_contract_threshold = 2 * 1024 * 1024 &redef;
 }
 
+@load base/bif/telemetry_functions.bif
+@load base/bif/telemetry_types.bif
+
 module Telemetry;
 export {
-
-	type MetricType: enum {
-		COUNTER,
-		GAUGE,
-		HISTOGRAM,
-	};
-
 	## Type that captures options used to create metrics.
 	type MetricOpts: record {
 		## The prefix (namespace) of the metric. Zeek uses the ``zeek``