Base/CI: Boot serenity in CI in a mode that runs tests on target

Build a new version of Serenity in CI that doesn't have all the debug
symbols on, or we'd be waiting a very long time to boot.

Insert a TestRunner entry into SystemServer.ini that will run a shell
script that runs tests in /bin and /usr/Tests and shuts down the system
in the new self-test boot mode. Also make sure enough basic services are
started in self-test such that the tests will actually run properly.

Base/etc/SystemServer.ini

@@ -4,7 +4,7 @@ SocketPermissions=660
 Lazy=1
 Priority=low
 User=protocol
-BootModes=text,graphical
+BootModes=text,graphical,self-test
 MultiInstance=1
 AcceptSocketConnections=1
 
@@ -39,13 +39,13 @@ Lazy=1
 Priority=low
 KeepAlive=1
 User=lookup
-BootModes=text,graphical
+BootModes=text,graphical,self-test
 
 [DHCPClient]
 Priority=low
 KeepAlive=1
 User=root
-BootModes=text,graphical
+BootModes=text,graphical,self-test
 
 [NotificationServer]
 Socket=/tmp/portal/notify
@@ -175,3 +175,11 @@ AcceptSocketConnections=1
 Executable=/bin/CrashDaemon
 KeepAlive=1
 User=anon
+
+[TestRunner@ttyS0]
+Executable=/home/anon/tests/run-tests-and-shutdown.sh
+StdIO=/dev/ttyS0
+Environment=DO_SHUTDOWN_AFTER_TESTS=1 TERM=xterm PATH=/bin:/usr/bin:/usr/local/bin
+User=anon
+WorkingDirectory=/home/anon
+BootModes=self-test

Base/home/anon/tests/run-tests-and-shutdown.sh

@@ -0,0 +1,30 @@
+#!/bin/sh
+
+echo "==== Running Tests on SerenityOS ===="
+
+run() {
+    test_cmd=($*)
+    echo "Running test -- $test_cmd"
+    if $test_cmd {
+        echo "::debug file=$test_cmd:: $test_cmd passed!"
+    } else {
+        echo "::error file=$test_cmd:: $test_cmd returned non-zero exit code, check logs!"
+    }
+}
+
+# TODO: It'd be nice to have a list+list op (as opposed to nest-on-in-another)
+# TODO: It'd be nice to have a list.length or enumerate(list) operation to allow terminal progress bar
+# TODO: test-web requires the window server
+system_tests=(test-js test-pthread test-compress (test-crypto bigint -t))
+# FIXME: Running too much at once is likely to run into #5541. Remove commented out find below when stable
+all_tests=($system_tests) #$(find /usr/Tests -type f | grep -v Kernel | grep -v .inc | shuf))
+
+for list in $all_tests {
+    for $list { run $it }
+}
+
+echo "==== Done running tests ===="
+
+if test $DO_SHUTDOWN_AFTER_TESTS {
+    shutdown -n
+}