Check |ro.vendor.api_level| for vendor API level on GRF/non-GRF chips

As ro.vendor.api_level available for both GRF/non-GRF chips.

Ref: https://source.android.com/docs/core/architecture/api-flags

Bug: 384693906
Bug: 365692904
Test: atest MicrodroidTests
Change-Id: Icc92b44a480bb27819818435403c42ada0d8889f
diff --git a/tests/helper/src/java/com/android/microdroid/test/device/MicrodroidDeviceTestBase.java b/tests/helper/src/java/com/android/microdroid/test/device/MicrodroidDeviceTestBase.java
index e6f15ff..74b88a7 100644
--- a/tests/helper/src/java/com/android/microdroid/test/device/MicrodroidDeviceTestBase.java
+++ b/tests/helper/src/java/com/android/microdroid/test/device/MicrodroidDeviceTestBase.java
@@ -259,11 +259,11 @@
     }
 
     /**
-     * @return The first vendor API level when the vendor images for an SoC that is qualified for
-     *     vendor freeze are first released with this property, or 0 if the property is not set.
+     * @return The vendor API level that the device as a whole must conform to, this value should be
+     *     available on both GRF and non-GRF devices.
      */
     protected static int getFirstVendorApiLevel() {
-        return SystemProperties.getInt("ro.board.first_api_level", 0);
+        return SystemProperties.getInt("ro.vendor.api_level", -1);
     }
 
     protected void assumeSupportedDevice() {