Add shortcut to reset video capture/encoding

Reset video capture/encoding on MOD+Shift+r.

Like on device rotation, this starts a new encoding session which
produces a video stream starting by a key frame.

PR #5432 <https://github.com/Genymobile/scrcpy/pull/5432>

app/src/control_msg.h

@@ -42,6 +42,7 @@ enum sc_control_msg_type {
     SC_CONTROL_MSG_TYPE_UHID_DESTROY,
     SC_CONTROL_MSG_TYPE_OPEN_HARD_KEYBOARD_SETTINGS,
     SC_CONTROL_MSG_TYPE_START_APP,
+    SC_CONTROL_MSG_TYPE_RESET_VIDEO,
 };
 
 enum sc_copy_key {