btest/coverage: Add record-fields test

Justin pointed out that the misc/dump-events test shows added fields to
the connection record. Add a new test that prints the connection record
recursively in bare and default mode to cover that use-case
specifically.

testing/btest/Baseline/coverage.record-fields/out.bare

@@ -0,0 +1,51 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+[zeek, -b, <...>/record-fields.zeek]
+connection {
+  * dpd: record DPD::Info, log=F, optional=T
+      DPD::Info {
+        * analyzer: string, log=T, optional=F
+        * failure_reason: string, log=T, optional=F
+        * id: record conn_id, log=T, optional=F
+            conn_id {
+              * orig_h: addr, log=T, optional=F
+              * orig_p: port, log=T, optional=F
+              * resp_h: addr, log=T, optional=F
+              * resp_p: port, log=T, optional=F
+             }
+        * proto: enum transport_proto, log=T, optional=F
+        * ts: time, log=T, optional=F
+        * uid: string, log=T, optional=F
+       }
+  * dpd_state: record DPD::State, log=F, optional=T
+      DPD::State {
+        * violations: table[count] of count, log=F, optional=F
+       }
+  * duration: interval, log=F, optional=F
+  * history: string, log=F, optional=F
+  * id: record conn_id, log=F, optional=F
+      conn_id { ... }
+  * inner_vlan: int, log=F, optional=T
+  * orig: record endpoint, log=F, optional=F
+      endpoint {
+        * flow_label: count, log=F, optional=F
+        * l2_addr: string, log=F, optional=T
+        * num_bytes_ip: count, log=F, optional=T
+        * num_pkts: count, log=F, optional=T
+        * size: count, log=F, optional=F
+        * state: count, log=F, optional=F
+       }
+  * resp: record endpoint, log=F, optional=F
+      endpoint { ... }
+  * service: set[string], log=F, optional=F
+  * service_violation: set[string], log=F, optional=T
+  * start_time: time, log=F, optional=F
+  * tunnel: vector of record Tunnel::EncapsulatingConn, log=F, optional=T
+      Tunnel::EncapsulatingConn {
+        * cid: record conn_id, log=T, optional=F
+            conn_id { ... }
+        * tunnel_type: enum Tunnel::Type, log=T, optional=F
+        * uid: string, log=T, optional=T
+       }
+  * uid: string, log=F, optional=F
+  * vlan: int, log=F, optional=T
+ }