Mark uwb apex data directory as system_server_data_dir

UWB stack needs to persist state inside it's apex directory.

Denial logs:
08-30 19:44:53.670  1635  1635 W queued-work-loo: type=1400 audit(0.0:9):
avc: denied { write } for name="com.android.uwb" dev="dm-40" ino=206
scontext=u:r:system_server:s0 tcontext=u:object_r:apex_module_data_file:s0
tclass=dir permissive=0

Bug: 197963882
Test: Verified shared preferences file creation/write under uwb
apex data directory.

Change-Id: Ic4925822ca7e01cd23aea6805c80720f2a3db9d7
diff --git a/private/file_contexts b/private/file_contexts
index 5433726..0c8bf78 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -575,6 +575,7 @@
 /data/misc/apexdata/com\.android\.compos(/.*)?        u:object_r:apex_compos_data_file:s0
 /data/misc/apexdata/com\.android\.permission(/.*)?    u:object_r:apex_system_server_data_file:s0
 /data/misc/apexdata/com\.android\.scheduling(/.*)?    u:object_r:apex_system_server_data_file:s0
+/data/misc/apexdata/com\.android\.uwb(/.*)?           u:object_r:apex_system_server_data_file:s0
 /data/misc/apexdata/com\.android\.wifi(/.*)?          u:object_r:apex_system_server_data_file:s0
 /data/misc/apexrollback(/.*)?   u:object_r:apex_rollback_data_file:s0
 /data/misc/apns(/.*)?           u:object_r:radio_data_file:s0