Fix progress API to have "output message" separate from task

A lot of our output is outside of a "task"; the Rust binding
incorrectly made it a method on `Progress`.  This is really
just a `println!()` that is backed by our dispatch system.

rust/src/lib.rs

@@ -280,6 +280,8 @@ pub mod ffi {
 
         fn progress_begin_task(msg: &str) -> UniquePtr<Progress>;
         fn end(self: Pin<&mut Progress>, msg: &str);
+
+        fn output_message(msg: &str);
     }
 
     // rpmostree-rpm-util.h

src/libpriv/rpmostree-output.cxx

@@ -124,16 +124,6 @@ progress_begin_task(const rust::Str msg) noexcept
   return std::make_unique<Progress>(ProgressType::TASK);
 }
 
-// Output a string.  Note that this should not be called when
-// a "task" is active.
-void 
-Progress::message(const rust::Str msg)
-{
-  auto msg_c = std::string(msg);
-  RpmOstreeOutputMessage task = { msg_c.c_str() };
-  active_cb (RPMOSTREE_OUTPUT_MESSAGE, &task, active_cb_opaque);
-}
-
 // When working on a task/percent/nitems, often we want to display a particular
 // item (such as a package).
 void 

src/libpriv/rpmostree-output.h

@@ -36,7 +36,6 @@ void output_message (rust::Str msg);
 struct Progress {
 public:
   void set_sub_message(rust::Str msg);
-  void message (rust::Str msg);
   void nitems_update(guint n);
   void percent_update(guint n);