Add river routing module

[weiyuan-jiang]

Add river routing module for offline land modeling (GEOSldas). Replaces #1023

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@YujiN, I am trying to bring back some codes in develop branch. The develop branch is not working as it is but I believe it would be more efficient. The runoff and the other variables are distributed as needed, which is way more efficient than allgatherV.

[weiyuan-jiang]

@zyj8881357 and @gmao-rreichle , I have made some changes:

1. Added a new catchment space which can be used in Internal ( restart) and History output. https://github.com/GEOS-ESM/GEOSgcm_GridComp/blob/3bf435f7614657329592c60f8b75509656e353a1/GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/GEOSland_GridComp/GEOSroute_GridComp/GEOS_RouteGridComp.F90#L722C5-L722C65

2. Added mapping from tile space to catchment space . https://github.com/GEOS-ESM/GEOSgcm_GridComp/blob/3bf435f7614657329592c60f8b75509656e353a1/GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/GEOSland_GridComp/GEOSroute_GridComp/GEOS_RouteGridComp.F90#L724C5-L724C67. It can be used here
   , which would replace the codes
   

3. Added subroutine to exchange downstream.

   GEOSgcm_GridComp/GEOSagcm_GridComp/GEOSphysics_GridComp/GEOSsurface_GridComp/GEOSland_GridComp/GEOSroute_GridComp/GEOS_RouteGridComp.F90

   Line 734 in 3bf435f

   call setup_exchange_cat(_RC)

   . It is zero-diff and quite efficient. It exchanges about 4 or 5 values each processor instead of 300K. It would be used
   here and replace the codes
   

4)Also all the outputs ( including check balance) and restarts will be replaced by the simple codes like this

[weiyuan-jiang]

To make further changes, we should start with make_bcs to produce necessary files

[weiyuan-jiang]

@zyj8881357 , I think this PR is ready for the test and comparison. To run this branch, you will need the develop branch of GEOSldas and feature/wjiang/pfaf_index of MAPL. Also please take a look at my run example in /discover/nobackup/wjiang/LDAS_exp/model/Routing
You will need three files : route_internal_rst, tile_pfaf.nc4 and river_input.nc
Please diff my LDAS.rc with yours and change yours accordingly to run the program. The route_internal_rst is not the same as yours. I am using the second day's restart (20140102 000000). You can create your own restart.

[gmao-rreichle]

cc @gmao-rreichle

[zyj8881357]

I have reviewed the branch and fixed several issues. It can now produce results that are nearly identical to those from my original branch (the remaining differences are likely due to numerical precision). In addition, I have updated the pre-processing script for the routing model so that it generates the files cellarea.nc and river_input.nc, which are used in make_bcs.