kernel: Add progress method to notifications

This commit is part of the libbitcoinkernel project and seeks to remove
the ChainstateManager's and, more generally, the kernel library's
dependency on interface_ui with options methods in this and the
following few commits. By removing interface_ui from the kernel library,
its dependency on boost is reduced to just boost::multi_index.

src/node/kernel_notifications.cpp

@@ -5,6 +5,7 @@
 #include <node/kernel_notifications.h>
 
 #include <node/interface_ui.h>
+#include <util/translation.h>
 
 namespace node {
 
@@ -18,4 +19,9 @@ void KernelNotifications::headerTip(SynchronizationState state, int64_t height,
     uiInterface.NotifyHeaderTip(state, height, timestamp, presync);
 }
 
+void KernelNotifications::progress(const bilingual_str& title, int progress_percent, bool resume_possible)
+{
+    uiInterface.ShowProgress(title.translated, progress_percent, resume_possible);
+}
+
 } // namespace node