Add uid field to SandboxSdkStorage atom

Uid field will be used to collect client app uid that makes calls to the
sandbox and be able to differentiate SDK storage information from different apps.

Bug: 247107418
Test: build passed
Eldar ID: 227133964

Change-Id: Iefe4b31390d2c9067011d9ec77313725c1b69c23
diff --git a/stats/atoms.proto b/stats/atoms.proto
index 186f2e0..53b7712 100644
--- a/stats/atoms.proto
+++ b/stats/atoms.proto
@@ -22790,6 +22790,9 @@
 
     // Storage
     optional int32 storage_kb = 2;
+
+    // Uid of the app that made a call to sandbox
+    optional int32 uid = 3 [(is_uid) = true];
 }
 
 /**