[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

Inizia individuando l’implementazione Android in share_plus in cui viene creato l’intent di condivisione, quindi esamina come l’activity di origine avvia il foglio di condivisione Android. Determina se il flag debba essere sempre applicato o esposto come opzione e verifica il comportamento risultante del selettore delle app rispetto al flusso di condivisione segnalato.

Scritto dal modello di indicizzazione a partire dal testo della issue.