Support IDM login

### Your use case

#### What would you like to do?

I'd like to login using IDM instead of plain username/password

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

My identity server only supports IDM login now, which prohibits me from using Element X, as I can't login.

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

Element (without X) supports this, I don't know whether any code can be reused from there.

### Have you considered any alternatives?

Login via QR code from desktop would be a workaround, but it says "Your account provider doesn't support signing into a new device with a QR code".

### Additional context

_No response_

### Are you willing to provide a PR?

No