Update UPP tag to upp_v8.2.0 for GFSv16.3.0

To support GFS V16.3 implementation, the UPP branch release/gfs_v16
was updated with the following changes:
1) aviation product upgrade
2) add continuous bucket precipitation product for wgne

Tag and update details provided by Wen Meng.

Refs: #744

Externals.cfg

@@ -22,7 +22,7 @@ protocol = git
 required = True
 
 [UPP]
-tag = upp_v8.1.2
+tag = upp_v8.2.0
 local_path = sorc/gfs_post.fd
 repo_url = https://github.com/NOAA-EMC/UPP.git
 protocol = git

sorc/checkout.sh

@@ -64,7 +64,7 @@ fi
 echo EMC_post checkout ...
 if [[ ! -d gfs_post.fd ]] ; then
     rm -f ${topdir}/checkout-gfs_post.log
-    git clone ${gtg_git_args:-} --branch upp_v8.1.2 https://github.com/NOAA-EMC/UPP.git gfs_post.fd >> ${topdir}/checkout-gfs_post.log 2>&1
+    git clone ${gtg_git_args:-} --branch upp_v8.2.0 https://github.com/NOAA-EMC/UPP.git gfs_post.fd >> ${topdir}/checkout-gfs_post.log 2>&1
     ################################################################################
     # checkout_gtg
     ## yes: The gtg code at NCAR private repository is available for ops. GFS only.