tests: Stop bundling "perf" tests with gnome-shell

Now that scripts are loaded as external modules, there's no reason
anymore for bundling them with the gnome-shell executable. Just
move the scripts into a dedicated folder in tests/ and run them
from there.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2812>

tests/shell/headlessStart.js

@@ -0,0 +1,107 @@
+// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
+/* eslint camelcase: ["error", { properties: "never", allow: ["^script_"] }] */
+
+const GLib = imports.gi.GLib;
+const MetaTest = imports.gi.MetaTest;
+const Shell = imports.gi.Shell;
+
+const Main = imports.ui.main;
+const Scripting = imports.ui.scripting;
+
+// This script tests that the shell handles connecting monitors after startup
+// is properly handled.
+
+export var METRICS = {};
+
+let _testMonitor = null;
+
+/**
+ * init:
+ */
+export function init() {
+    global.connect('shutdown', () => {
+        _testMonitor?.destroy();
+    });
+    GLib.timeout_add_seconds(
+        GLib.PRIORITY_LOW, 2,
+        () => {
+            log('Connecting 1280x720 test monitor');
+            _testMonitor = MetaTest.TestMonitor.new(
+                global.context, 1280, 720, 60.0);
+        });
+    Scripting.defineScriptEvent('monitorsChanged', 'Monitors changed');
+
+    const display = global.display;
+    console.assert(display.get_n_monitors() === 0, 'Not running headless');
+
+    const monitorManager = global.backend.get_monitor_manager();
+    const monitorsChangedHandlerId = monitorManager.connect('monitors-changed',
+        () => {
+            console.assert(display.get_n_monitors() === 1,
+                'Expected a single monitor');
+            Scripting.scriptEvent('monitorsChanged');
+            monitorManager.disconnect(monitorsChangedHandlerId);
+        });
+    Shell.PerfLog.get_default().set_enabled(true);
+}
+
+/**
+ * run:
+ */
+export async function run() {
+    /* eslint-disable no-await-in-loop */
+    Scripting.defineScriptEvent('overviewShowDone', 'Overview finished showing');
+    Scripting.defineScriptEvent('overviewHideDone', 'Overview finished hiding');
+
+    Main.overview.connect('shown',
+        () => Scripting.scriptEvent('overviewShowDone'));
+    Main.overview.connect('hidden',
+        () => Scripting.scriptEvent('overviewHideDone'));
+
+    Main.overview.hide();
+    await Scripting.waitLeisure();
+
+    Main.overview.show();
+    await Scripting.waitLeisure();
+
+    /* eslint-enable no-await-in-loop */
+}
+
+let monitorsChanged = false;
+let overviewHidden = false;
+let overviewShown = false;
+
+/**
+ * script_monitorsChanged:
+ */
+export function script_monitorsChanged() {
+    monitorsChanged = true;
+}
+
+/**
+ * script_overviewHideDone:
+ */
+export function script_overviewHideDone() {
+    overviewHidden = true;
+}
+
+/**
+ * script_overviewShowDone:
+ */
+export function script_overviewShowDone() {
+    overviewShown = true;
+}
+
+/**
+ * finish:
+ */
+export function finish() {
+    if (!monitorsChanged)
+        throw new Error('Monitors never changed');
+
+    if (!overviewHidden)
+        throw new Error('Failed to hide overview');
+
+    if (!overviewShown)
+        throw new Error('Failed to show overview');
+}