added gmm-tree override to transition zone grids

stable-crust/grid/system-stable/gmm-config.json

+{
+  "max-distance": 300.0
+}

stable-crust/grid/system-stable/gmm-tree.json

+[
+  { "id": "NGA_EAST_2023", "weight": 0.16665 },
+  { "id": "NGA_EAST_2023_ADJUSTED", "weight": 0.16665 },
+  { "id": "NGA_EAST_SEEDS_2023", "weight": 0.08335 },
+  { "id": "NGA_EAST_SEEDS_2023_ADJUSTED", "weight": 0.08335 },
+  { "id": "ASK_14_BASIN", "weight": 0.125 },
+  { "id": "BSSA_14_BASIN", "weight": 0.125 },
+  { "id": "CB_14_BASIN", "weight": 0.125 },
+  { "id": "CY_14_BASIN", "weight": 0.125 }  
+]