Auto generate userdata.img

Test: CI and unit tests
Bug: 377563861
Change-Id: I42582db31377600412d2acf0dceab5ee9e15bc58
diff --git a/fsgen/filesystem_creator.go b/fsgen/filesystem_creator.go
index c9bbf3f..bcf2361 100644
--- a/fsgen/filesystem_creator.go
+++ b/fsgen/filesystem_creator.go
@@ -130,6 +130,9 @@
 	if android.InList("odm", generatedPartitionTypes) {
 		partitionProps.Odm_partition_name = proptools.StringPtr(generatedModuleNameForPartition(ctx.Config(), "odm"))
 	}
+	if android.InList("userdata", f.properties.Generated_partition_types) {
+		partitionProps.Userdata_partition_name = proptools.StringPtr(generatedModuleNameForPartition(ctx.Config(), "userdata"))
+	}
 	partitionProps.Vbmeta_partitions = vbmetaPartitions
 
 	ctx.CreateModule(filesystem.AndroidDeviceFactory, baseProps, partitionProps)
@@ -202,6 +205,8 @@
 			},
 		}
 		fsProps.Base_dir = proptools.StringPtr("odm")
+	case "userdata":
+		fsProps.Base_dir = proptools.StringPtr("data")
 
 	}
 }