[Request]: Specify Intent.FLAG_ACTIVITY_NEW_TASK for sharing

### Plugin

share_plus

### Use case

I am experiencing a behavior where sharing via the Android share sheet causes the target app to be displayed it the same app switcher entry as the originating app. From my research, this is because the sharing intent is not created with the `Intent.FLAG_ACTIVITY_NEW_TASK` flag. If we could optionally (or always) pass this flag when sharing, I believe that would make the flow much more intuitive for users.

### Proposal

Have an option to (or just always) set `Intent.FLAG_ACTIVITY_NEW_TASK` when creating the share intent on Android.

### Expected behavior

This is sharing from Keep to Drive, and it works as expected.

https://github.com/fluttercommunity/plus_plugins/assets/7417301/3fc7a343-7d9e-4de5-a52b-863ec66a7a07

### Current behavior

This is sharing from Thunder (which uses `share_plus`) to Drive, and it does not work as expected.

https://github.com/fluttercommunity/plus_plugins/assets/7417301/0ec0877f-ba8b-47ac-a2b9-b351f1ccb1ec

Beginne damit, die Android-Implementierung in share_plus zu lokalisieren, in der der Sharing-Intent erstellt wird, und untersuche anschließend, wie die aufrufende Activity das Android-Share-Sheet startet. Kläre, ob das Flag immer angewendet oder als Option verfügbar gemacht werden sollte, und überprüfe das daraus resultierende Verhalten des App-Umschalters anhand des gemeldeten Sharing-Ablaufs.

Vom Indexierungsmodell aus dem Issue-Text verfasst.