[incremental] labels for incfs and directory root

Adding two labels: "incfs" for the incremental filesystem and
"incremental_root_file" for file paths /data/incremental/*.

Doc: go/incremental-selinux

Test: manual
Change-Id: I7d45ed1677e3422119b2861dfc7b541945fcb7a2
diff --git a/private/file_contexts b/private/file_contexts
index 80f7f75..65d0e6f 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -481,6 +481,7 @@
 /data/app-private/vmdl.*\.tmp(/.*)?   u:object_r:apk_private_tmp_file:s0
 /data/gsi(/.*)?        u:object_r:gsi_data_file:s0
 /data/gsi/ota(/.*)?    u:object_r:ota_image_data_file:s0
+/data/incremental(/.*)?   u:object_r:incremental_root_file:s0
 /data/tombstones(/.*)?	u:object_r:tombstone_data_file:s0
 /data/vendor/tombstones/wifi(/.*)? u:object_r:tombstone_wifi_data_file:s0
 /data/local/tmp(/.*)?	u:object_r:shell_data_file:s0