aconfig: remove calls to unwrap (outside tests)

Do not call unwrap outside tests: replace existing uses with Result
return values or infallible alternatives.

Bug: 279485059
Test: atest aconfig.test
Change-Id: Ie5919b704b23a0f96bbef84ffbe9270d667cecd8
diff --git a/tools/aconfig/src/cache.rs b/tools/aconfig/src/cache.rs
index 7b6edc5..5ef1829 100644
--- a/tools/aconfig/src/cache.rs
+++ b/tools/aconfig/src/cache.rs
@@ -119,6 +119,10 @@
     pub fn into_iter(self) -> impl Iterator<Item = Item> {
         self.items.into_iter()
     }
+
+    pub fn namespace(&self) -> &str {
+        &self.namespace
+    }
 }
 
 #[cfg(test)]