Move the Mark All As Read button to the Advanced Settings screen.

### Your use case

#### What would you like to do?

Element X currently has a Mark All As Read button hidden away in the Developer Options screen. It would be nice if this could become an official feature and moved to the Advanced Settings screen.

#### Why would you like to do it?

The button was added as a technical workaround for stuck notifications (hence being in Developer Options) but that requires users of the stable app versions to know the 7-tap trick to reveal those.

Additionally this button was available in Classic and is a way to declare "notification bankruptcy" for users without having to manually open every room after e.g. returning from holidays.

#### How would you like to achieve it?

Tidy up the implementation (queue the requests to help with rate limiting and possibly publish the progress).

### Have you considered any alternatives?

Not adding it, which is fine but results in more users learning about our feature flags for incomplete features which feels less than ideal.

### Additional context

_No response_

Start by locating the existing Mark All As Read button in Element X's Developer Options and trace how its requests are handled. Review the settings placement and notification behavior, then confirm that the button is available under Advanced Settings, requests are queued for rate limiting, and progress is communicated if implemented.

Written by the indexing model from the issue text.