Rename ART run-tests `expected.txt` files as `expected-stdout.txt`.

This is in preparation for the addition of `expected-stderr.txt` files
in all ART run-test directories, which will record the expected
standard error for each of these tests, and which will be verified
along with `expected-stdout.txt`.

Test: Run ART run-tests on host and device using `testrunner.py`.
Test: atest --test-mapping art:all
Bug: 171865375
Bug: 147812905
Change-Id: I37e3c4b8409475790e2fc63514cdf57156d47ff4
diff --git a/test/run-test b/test/run-test
index 83897c5..e51d9f8 100755
--- a/test/run-test
+++ b/test/run-test
@@ -122,7 +122,7 @@
 info="info.txt"
 build="build"
 run="run"
-expected="expected.txt"
+expected="expected-stdout.txt"
 check_cmd="check"
 output="output.txt"
 build_output="build-output.txt"
@@ -764,7 +764,7 @@
         echo "              The script will only run the test portion, and " \
              "share oat and dex files."
         echo "  $prog --update [options] [test-name]  Update mode" \
-             "(replaces expected.txt)."
+             "(replaces expected-stdout.txt)."
         echo '  Omitting the test name or specifying "-" will use the' \
              "current directory."
         echo "  Runtime Options:"
@@ -1129,7 +1129,7 @@
         $maybe_device_mode \
         --raw-cmd="$raw_cmd" \
         --check-script="$cwd/check" \
-        --expected-output="$cwd/expected.txt" \
+        --expected-output="$cwd/expected-stdout.txt" \
         --logfile="$cwd/bisection_log.txt" \
         --timeout=${timeout:-300}
     fi