Add option to force-stop app before starting

The previous commit introduced:

    scrcpy --start-app=name

By adding a '+' prefix, the app is stopped beforehand:

    scrcpy --start-app=+name

This is especially useful to start it on a new virtual display:

    scrcpy --new-display --start-app=+firefox

app/scrcpy.1

@@ -497,6 +497,10 @@ Default is "lalt,lsuper" (left-Alt or left-Super).
 .BI "\-\-start\-app " name
 Start an Android app, by its exact package name or the start of its name (case-insensitive).
 
+Add a '+' prefix to force-stop before starting the app:
+
+    scrcpy --new-display --start-app=+firefox
+
 .TP
 .B \-t, \-\-show\-touches
 Enable "show touches" on start, restore the initial value on exit.

app/src/cli.c

@@ -811,7 +811,9 @@ static const struct sc_option options[] = {
         .longopt = "start-app",
         .argdesc = "name",
         .text = "Start an Android app, by its exact package name or the start "
-                "of its name (case-insensitive).",
+                "of its name (case-insensitive).\n"
+                "Add a '+' prefix to force-stop before starting the app:\n"
+                "    scrcpy --new-display --start-app=+firefox",
     },
     {
         .shortopt = 't',

server/src/main/java/com/genymobile/scrcpy/control/Controller.java

@@ -584,6 +584,11 @@ private int getActionDisplayId() {
     }
 
     private void startApp(String name) {
+        boolean forceStopBeforeStart = name.startsWith("+");
+        if (forceStopBeforeStart) {
+            name = name.substring(1);
+        }
+
         List<DeviceApp> apps = Device.findApps(name);
         if (apps.isEmpty()) {
             Ln.w("No app found for name \"" + name + "\"");
@@ -604,7 +609,7 @@ private void startApp(String name) {
         }
 
         Ln.i("Starting app \"" + app.getName() + "\" [" + app.getPackageName() + "] on display " + startAppDisplayId + "...");
-        Device.startApp(app.getPackageName(), startAppDisplayId);
+        Device.startApp(app.getPackageName(), startAppDisplayId, forceStopBeforeStart);
     }
 
     private int getStartAppDisplayId() {

server/src/main/java/com/genymobile/scrcpy/device/Device.java

@@ -270,7 +270,7 @@ private static List<DeviceApp> findStartingByName(PackageManager pm, List<Applic
     }
 
     @TargetApi(Build.VERSION_CODES.O)
-    public static void startApp(String packageName, int displayId) {
+    public static void startApp(String packageName, int displayId, boolean forceStop) {
         Intent launchIntent = FakeContext.get().getPackageManager().getLaunchIntentForPackage(packageName);
         if (launchIntent == null) {
             Ln.w("Cannot create launch intent for app " + packageName);
@@ -283,6 +283,9 @@ public static void startApp(String packageName, int displayId) {
         launchOptions.setLaunchDisplayId(displayId);
 
         ActivityManager am = ServiceManager.getActivityManager();
+        if (forceStop) {
+            am.forceStopPackage(packageName);
+        }
         am.startActivity(launchIntent, launchOptions.toBundle());
     }