OpaqueVal: Register TelemetryVals, too

Even if they are not serializable, OpaqueMgr::TypeID() is called
during BuildJSON() for them and that previously just aborted.

Closes #3473

testing/btest/coverage/global-ids-to-json.zeek

@@ -0,0 +1,8 @@
+# @TEST-DOC: Ensure to_json(global_ids()) does not abort and do not expect any stderr output.
+# @TEST-EXEC: unset ZEEK_ALLOW_INIT_ERRORS; zeek %INPUT
+# @TEST-EXEC: btest-diff .stderr
+
+event zeek_init()
+	{
+	assert |to_json(global_ids())| > 0;
+	}