Add app action to trigger auto-upload

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**Is your feature request related to a problem? Please describe.**
I am struggling with battery usage on the Nextcloud Android app. I know the team is already working on this, and are doing a fantastic job, so this is not a question of battery usage per se. But I'd like to be able to turn on the normal battery optimisations and still be sure that the auto-upload functionality is working reliably.

**Describe the solution you'd like**
I'd love to see an App Action added to the app that can trigger the auto-upload functionality directly.

What I'd like to do is add a routine or task with conditions (in my case, when the phone is charging and connected to WiFi, and between certain hours), which then runs the auto-upload intent. Then I needn't be concerned if Android kills the app to save battery when the phone isn't connected to power.

I realise that this is quite a hack, and won't be accessible to many users. However, I'm hoping that it won't take a great deal of work to expose the intent as an app action.

Thank you!