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.

src/NetVar.h

@@ -105,4 +105,6 @@ extern void init_builtin_types();
 #include "packet_analysis.bif.netvar_h"
 #include "reporter.bif.netvar_h"
 #include "supervisor.bif.netvar_h"
+#include "telemetry_consts.bif.netvar_h"
+#include "telemetry_types.bif.netvar_h"
 #include "types.bif.netvar_h"