Add import & export section in the settings menu

[peat80]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

Add new menu section: Import & Export

Why do you want this feature?

While trying some different prs or do (re-)installs on various devices i often want to import my previous settings and / or a database backup.

To do this you have to go trough the settings and scroll trough to find the import entry which is time consuming.

An extra menu section would make such tasks way faster.

Additional information

I would propose to add a *import & export" settings section with the following content:

Import database
Import previous subscriptions export
Import subscriptions from YouTube
Import subscriptions from Soundcloud

Export database
Export subscriptions

[opusforlife2]

Related: #3192.

[killerrook]

Maybe instead of import and export the section should be named backup and restore 'cause I believe that users are more familiar with backup and restore

[opusforlife2]

Or both, even.

[peat80]

Then maybe backup and import? 🤔😁

I'm sure a good fitting name will be found.

#9236 should probably also fit well in this new category. 🤔