Add next-hop-group-member hardware object selector

Summary:
Add `HwObjectType::NEXT_HOP_GROUP_MEMBER` and map it to `SAI_OBJECT_TYPE_NEXT_HOP_GROUP_MEMBER`, allowing `fboss2 show hw-object` to retrieve next-hop-group-member objects independently. Add CLI argument parsing coverage for the new enum value.

landed-with-radar-review

Reviewed By: shri-khare

Differential Revision: D116091695

fbshipit-source-id: 166d20f2cf9cd6aa1498a8a84f3720336b49b7c9

Author: jasmeetbagga

fboss/agent/hw/sai/switch/SaiSwitch.cpp

@@ -5125,6 +5125,9 @@ std::string SaiSwitch::listObjects(
         objTypes.push_back(SAI_OBJECT_TYPE_NEXT_HOP_GROUP);
         objTypes.push_back(SAI_OBJECT_TYPE_NEXT_HOP_GROUP_MEMBER);
         break;
+      case HwObjectType::NEXT_HOP_GROUP_MEMBER:
+        objTypes.push_back(SAI_OBJECT_TYPE_NEXT_HOP_GROUP_MEMBER);
+        break;
       case HwObjectType::ROUTER_INTERFACE:
         objTypes.push_back(SAI_OBJECT_TYPE_ROUTER_INTERFACE);
         break;

fboss/agent/if/ctrl.thrift

@@ -768,6 +768,7 @@ enum HwObjectType {
   SYSTEM_PORT = 25,
   FIRMWARE = 26,
   SRV6 = 27,
+  NEXT_HOP_GROUP_MEMBER = 28,
 }
 
 exception FbossFibUpdateError {

fboss/cli/fboss2/test/CmdArgsTest.cpp

@@ -136,6 +136,10 @@ TEST(CmdArgsTest, HwObjectList) {
   ASSERT_NO_THROW(utils::HwObjectList({"PORT"}));
   EXPECT_THAT(
       utils::HwObjectList({"PORT"}).data(), ElementsAre(HwObjectType::PORT));
+  ASSERT_NO_THROW(utils::HwObjectList({"NEXT_HOP_GROUP_MEMBER"}));
+  EXPECT_THAT(
+      utils::HwObjectList({"NEXT_HOP_GROUP_MEMBER"}).data(),
+      ElementsAre(HwObjectType::NEXT_HOP_GROUP_MEMBER));
   ASSERT_NO_THROW(utils::HwObjectList({"LAG", "MIRROR"}));
   EXPECT_THAT(
       utils::HwObjectList({"LAG", "MIRROR"}).data(),