Simplify printing to use standard stream

Author: thk123

regression/cbmc-incr-oneloop/alarm2/test-json-output.desc

@@ -4,6 +4,6 @@ main.c
 ^EXIT=10$
 ^SIGNAL=0$
 "messageText": "VERIFICATION FAILED"
-"currentUnwinding": 1
+"current-unwinding": "1"
 --
 ^warning: ignoring

regression/cbmc-incr-oneloop/alarm2/test.desc

@@ -1,7 +1,7 @@
 CORE
 main.c
 --incremental-loop main.0 --unwind-min 5 --unwind-max 10
-Current unwinding: 1
+current-unwinding: 1
 ^EXIT=10$
 ^SIGNAL=0$
 ^VERIFICATION FAILED$

src/goto-checker/symex_bmc_incremental_one_loop.cpp

@@ -137,27 +137,7 @@ bool symex_bmc_incremental_one_loopt::resume(
 }
 void symex_bmc_incremental_one_loopt::log_unwinding(unsigned unwind)
 {
-  const std::string unwind_num = std::to_string(unwind);
-  switch(output_ui)
-  {
-  case ui_message_handlert::uit::PLAIN:
-  {
-    log.statistics() << "Current unwinding: " << unwind_num << messaget::eom;
-    break;
-  }
-  case ui_message_handlert::uit::XML_UI:
-  {
-    xmlt xml("current-unwinding");
-    xml.data = unwind_num;
-    log.statistics() << xml << messaget::eom;
-    break;
-  }
-  case ui_message_handlert::uit::JSON_UI:
-  {
-    json_objectt json;
-    json["currentUnwinding"] = json_numbert(unwind_num);
-    log.statistics() << json << messaget::eom;
-    break;
-  }
-  }
+  xmlt data{"current-unwinding"};
+  data.data = std::to_string(unwind);
+  log.statistics() << data;
 }