Add `avb_custom_vbmeta_images_partition_list` to misc_info.txt

Make generates this from `BOARD_AVB_VBMETA_CUSTOM_PARTITIONS`. To
generate this in Soong, a new Filesytem_partition_type is added to
vbmeta modules. For the chained vbmeta partitions for cuttlefish, this
will be
- system
- vendor
- system_dlkm
- vendor_dlkm

android_device will query this information from its vbmeta partitions,
and filter out system and vendor.

Bug: 398036609
Test: Built and diff'd misc_info.txt locally
Change-Id: I8ff3fe5e5e50504e49abbf89f7d50be472e64e30
diff --git a/fsgen/vbmeta_partitions.go b/fsgen/vbmeta_partitions.go
index 11f4bd0..594c404 100644
--- a/fsgen/vbmeta_partitions.go
+++ b/fsgen/vbmeta_partitions.go
@@ -76,6 +76,7 @@
 	var chainedPartitionTypes []string
 	for _, chainedName := range android.SortedKeys(partitionVars.ChainedVbmetaPartitions) {
 		props := partitionVars.ChainedVbmetaPartitions[chainedName]
+		filesystemPartitionType := chainedName
 		chainedName = "vbmeta_" + chainedName
 		if len(props.Partitions) == 0 {
 			continue
@@ -123,13 +124,14 @@
 			filesystem.VbmetaFactory,
 			".", // Create in the root directory for now so its easy to get the key
 			&filesystem.VbmetaProperties{
-				Partition_name:          proptools.StringPtr(chainedName),
-				Stem:                    proptools.StringPtr(chainedName + ".img"),
-				Private_key:             proptools.StringPtr(props.Key),
-				Algorithm:               &props.Algorithm,
-				Rollback_index:          rollbackIndex,
-				Rollback_index_location: &ril,
-				Partitions:              proptools.NewSimpleConfigurable(partitionModules),
+				Partition_name:            proptools.StringPtr(chainedName),
+				Filesystem_partition_type: proptools.StringPtr(filesystemPartitionType),
+				Stem:                      proptools.StringPtr(chainedName + ".img"),
+				Private_key:               proptools.StringPtr(props.Key),
+				Algorithm:                 &props.Algorithm,
+				Rollback_index:            rollbackIndex,
+				Rollback_index_location:   &ril,
+				Partitions:                proptools.NewSimpleConfigurable(partitionModules),
 			}, &struct {
 				Name *string
 			}{