Modem ML: Add sepolicy for TFLiteService

Add the sepolicy required to:
- Introduce modemml_tflite_service which runs on the system server.
- Allow modem_ml_svc_sit to access the new service.
- Allow system_server to access NNAPI TPU service.

Relevant logs before the sepolicy changes are made:

```
auditd  : avc:  denied  { find } for pid=1000 uid=1001 name=com.android.server.modemml.ITFLiteService/default scontext=u:r:modem_ml_svc_sit:s0 tcontext=u:object_r:modemml_tflite_service:s0 tclass=service_manager permissive=1
```

```
11-14 03:03:44.392  1064  1064 I auditd  : type=1400 audit(0.0:9): avc:  denied  { call } for  comm="modem_ml_svc_si" scontext=u:r:modem_ml_svc_sit:s0 tcontext=u:r:system_server:s0 tclass=binder permissive=1
```

```
SELinux : avc:  denied  { find } for pid=1115 uid=1000 name=android.hardware.neuralnetworks.IDevice/google-edgetpu scontext=u:r:system_server:s0 tcontext=u:object_r:edgetpu_nnapi_service:s0 tclass=service_manager permissive=1
```

Bug: 307449478

Change-Id: I14c2aa02eca08a026d100af6eea11ac9ac9e4fc7

vendor/service.te

@@ -4,3 +4,4 @@ type hal_uwb_vendor_service, service_manager_type, hal_service_type;
 # WLC
 type hal_wireless_charger_service, hal_service_type, protected_service, service_manager_type;
 
+type modemml_tflite_service, system_server_service, service_manager_type;

vendor/service_contexts

@@ -3,3 +3,4 @@ com.google.hardware.pixel.display.IDisplay/default                u:object_r:hal
 vendor.google.wireless_charger.IWirelessCharger/default           u:object_r:hal_wireless_charger_service:s0
 hardware.qorvo.uwb.IUwbVendor/default                             u:object_r:hal_uwb_vendor_service:s0
 android.hardware.media.c2.IComponentStore/default1                u:object_r:hal_codec2_service:s0
+com.android.server.modemml.ITFLiteService/default                 u:object_r:modemml_tflite_service:s0

vendor/system_server.te

@@ -0,0 +1,2 @@
+# Allow modemml.TFLiteService in system server to access NNAPI TPU service
+allow system_server edgetpu_nnapi_service:service_manager find;