guest: trusty: test_vm*: support collecting the VM console log

- also remove TEST_MAPPING as it actually is not used
- add instructions in README

Bug: 367423387
Test: atest VtsSeeHalTargetTest
Change-Id: Ia7b19b83ec9ac135d70af81debbd8516c364dd00
diff --git a/guest/trusty/test_vm/trusty-vm-launcher.sh b/guest/trusty/test_vm/trusty-vm-launcher.sh
index cb8661f..079a66a 100755
--- a/guest/trusty/test_vm/trusty-vm-launcher.sh
+++ b/guest/trusty/test_vm/trusty-vm-launcher.sh
@@ -14,4 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-/apex/com.android.virt/bin/vm run /data/local/tmp/trusty_test_vm/trusty-test_vm-config.json
+mkdir -p /data/local/tmp/trusty_test_vm/logs || true
+/apex/com.android.virt/bin/vm run \
+   --console /data/local/tmp/trusty_test_vm/logs/console.log \
+   /data/local/tmp/trusty_test_vm/trusty-test_vm-config.json