enhance: use mmap prefix to define all mmap related configs (#31436)

Signed-off-by: sunby <sunbingyi1992@gmail.com>

configs/milvus.yaml

@@ -356,7 +356,8 @@ queryNode:
       taskQueueExpire: 60 # 1 min by default, expire time of inner user task queue since queue is empty.
       enableCrossUserGrouping: false # false by default Enable Cross user grouping when using user-task-polling policy. (close it if task of any user can not merge others).
       maxPendingTaskPerUser: 1024 # 50 by default, max pending task in scheduler per user.
-  mmapEnabled: false # enable mmap global, if set true, will use mmap to load segment data
+  mmap:
+    mmapEnabled: false # enable mmap global, if set true, will use mmap to load segment data
 
   # can specify ip for example
   # ip: 127.0.0.1

pkg/util/paramtable/component_param.go

@@ -2205,17 +2205,19 @@ func (p *queryNodeConfig) init(base *BaseTable) {
 	p.CacheEnabled.Init(base.mgr)
 
 	p.MmapDirPath = ParamItem{
-		Key:          "queryNode.mmapDirPath",
+		Key:          "queryNode.mmap.mmapDirPath",
 		Version:      "2.3.0",
 		DefaultValue: "",
+		FallbackKeys: []string{"queryNode.mmapDirPath"},
 		Doc:          "The folder that storing data files for mmap, setting to a path will enable Milvus to load data with mmap",
 	}
 	p.MmapDirPath.Init(base.mgr)
 
 	p.MmapEnabled = ParamItem{
-		Key:          "queryNode.mmapEnabled",
+		Key:          "queryNode.mmap.mmapEnabled",
 		Version:      "2.4.0",
 		DefaultValue: "false",
+		FallbackKeys: []string{"queryNode.mmapEnabled"},
 		Doc:          "Enable mmap for loading data",
 	}
 	p.MmapEnabled.Init(base.mgr)