[PLAT-15799]Create a 2024.2/gflag_groups.json for 2024.2 releases

Summary: Add gflag groups file for both 2.25 and 2024.2

Test Plan: Create universe on 2024.2 and check if the correct flags are enabled for the feature `Enhanced Postgres Compatibility`

Reviewers: nbhatia, yshchetinin, sneelakantan

Reviewed By: yshchetinin

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D39293

Author: Deepti-yb

managed/src/main/resources/gflag_groups/2.25/gflag_groups.json

@@ -0,0 +1,13 @@
+[
+    {
+        "group_name": "ENHANCED_POSTGRES_COMPATIBILITY",
+        "flags": {
+            "MASTER": {},
+            "TSERVER": {
+                "yb_enable_read_committed_isolation": "true",
+                "ysql_enable_read_request_caching": "true",
+                "ysql_pg_conf_csv": "yb_enable_base_scans_cost_model=true,yb_enable_optimizer_statistics=true,yb_bnl_batch_size=1024,yb_enable_bitmapscan=true,yb_use_hash_splitting_by_default=false"
+            }
+        }
+    }
+]

managed/src/main/resources/gflag_groups/2024.2/gflag_groups.json

@@ -0,0 +1,13 @@
+[
+    {
+        "group_name": "ENHANCED_POSTGRES_COMPATIBILITY",
+        "flags": {
+            "MASTER": {},
+            "TSERVER": {
+                "yb_enable_read_committed_isolation": "true",
+                "ysql_enable_read_request_caching": "true",
+                "ysql_pg_conf_csv": "yb_enable_base_scans_cost_model=true,yb_enable_optimizer_statistics=true,yb_bnl_batch_size=1024,yb_enable_bitmapscan=true,yb_use_hash_splitting_by_default=false"
+            }
+        }
+    }
+]