Move better keep inventory configs to seperate datapack

Fixes issue with BKI being loaded above the mc_rebalance datapack when
updating an existing world to a version with the BKI datapack

overrides/resources/common/required/z_bki_override/pack.mcmeta

@@ -0,0 +1,7 @@
+{
+  "pack": {
+    "description":"Made to have a higher load order than better keep inventory",
+    "pack_format": 48,
+    "supported_formats": [34, 48]
+  }
+}