Add Error callback from Offload HAL

Error callback to report errors in Offload HAL service. Included VTS
tests to verify these callbacks are invoked.

Bug: 32842314
Test: Unit tests
Change-Id: I389b28b6ed5db7782ce6425beae67f5bdc2cf4aa
diff --git a/wifi/offload/1.0/IOffloadCallback.hal b/wifi/offload/1.0/IOffloadCallback.hal
index 4599370..4888125 100644
--- a/wifi/offload/1.0/IOffloadCallback.hal
+++ b/wifi/offload/1.0/IOffloadCallback.hal
@@ -22,4 +22,11 @@
      * @param scanResult a vector of scan result objects
      */
     oneway onScanResult(vec<ScanResult> scanResult);
+    /**
+     * Interface for the Offload HAL to inform the client of error conditions
+     * see OffloadStatus for the error conditions to be reported
+     *
+     * @param status OffloadStatus
+     */
+    oneway onError(OffloadStatus status);
 };