Add seacas patch to support Pamgen as a TriBITS external compliant pa… (#508)

* Add seacas patch to support Pamgen as a TriBITS external compliant package.

* Apply patch and remove the patch file since modern tribits supports both use cases of building SEACAS and Pamgen as TriBITS packages and building Pamgen as a TriBITS external compliant package within seacas.

Author: tonnguy

TPLsList.cmake

@@ -68,7 +68,7 @@ SET( Seacas_TPLS_FINDMODS_CLASSIFICATIONS
   DataWarp        "cmake/TPLs/"    SS
   METIS           "cmake/TPLs/"    SS
   ParMETIS        "cmake/TPLs/"    SS
-  Pamgen          "cmake/TPLs/"    SS
+  Pamgen          "TRIBITS_PKG"    SS
   Matio           "cmake/TPLs/"    SS
   CUDA            "cmake/TPLs/"    SS
   Kokkos          "${${PROJECT_NAME}_TRIBITS_DIR}/common_tpls/"  SS