Add cpuset system group

Set cpuset system group to little and mid cores only when screen
off.

Bug: 328210236
Test: build pass
Change-Id: Iab441032d57c4f4a3efefb5f8ce51dae4a63e9aa

powerhint-comet.json

@@ -311,6 +311,16 @@
       "DefaultIndex": 0,
       "ResetOnInit": true
     },
+    {
+      "Name": "SystemCpuset",
+      "Path": "/dev/cpuset/system/cpus",
+      "Values": [
+        "0-7",
+        "0-6"
+      ],
+      "DefaultIndex": 0,
+      "ResetOnInit": true
+    },
     {
       "Name": "FGCpuset",
       "Path": "/dev/cpuset/foreground/cpus",
@@ -2541,6 +2551,12 @@
       "Type": "EndHint",
       "Value": "DISPLAY_UPDATE_IMMINENT"
     },
+    {
+      "PowerHint": "DISPLAY_IDLE",
+      "Node": "SystemCpuset",
+      "Duration": 0,
+      "Value": "0-6"
+    },
     {
       "PowerHint": "DISPLAY_UPDATE_IMMINENT",
       "Node": "CPULittleClusterDownRateLimitUs",