Add an ostream formatter for StackTraceError

Bug: b/471297333

Author: Databean

base/cvd/cuttlefish/result/error_type.cc

@@ -16,6 +16,7 @@
 #include "cuttlefish/result/error_type.h"
 
 #include <optional>
+#include <ostream>
 #include <sstream>
 #include <string>
 #include <utility>
@@ -210,6 +211,10 @@ std::string ResultErrorFormat(bool color) {
   return "{:" + fmt_str + "}";
 }
 
+std::ostream& operator<<(std::ostream& out, const StackTraceError& error) {
+  return out << error.FormatForEnv();
+}
+
 }  // namespace cuttlefish
 
 fmt::format_context::iterator

base/cvd/cuttlefish/result/error_type.h

@@ -211,6 +211,8 @@ inline StackTraceEntry::operator android::base::expected<T,
   return android::base::unexpected(std::move(*this));
 }
 
+std::ostream& operator<<(std::ostream&, const StackTraceError&);
+
 }  // namespace cuttlefish
 
 /**