MN Sediment - Add FDCTM streamflow selection

[amedenblik]

Parent issue is #1544

Related to #1919 and #1545

Currently, users can select a gage to use that gage's streamflow as an input to the sediment model. Rather than use a gage's streamflow, the user may want to estimate streamflow at an ungaged location by using the Flow Duration Curve Transfer Method (FDCTM).

• Allow the user to indicate in the modal that they would like to use the FDCTM method to estimate streamflow. The user will need to select a reference gage from which to estimate the streamflow.
• We will probably want to discuss this user interface in more detail