[flexiglass] Fix blurry user switcher icon for default image

The UserSwitcherInteractor serves the user's image as Drawable. In case the user doesn't have an image, it serves a vector graphic as Drawable as default.
Later on, when we want to draw the user's image in the UI for the user switcher on bouncer, we generate a bitmap out of the Drawable in BouncerOverlayContentViewModel. Without providing a desired size, the resulting bitmap has 48x48px resolution. The displayed image however has a size of 190dp, resulting in the vector graphic being displayed as an upscaled and pixelated image.

This CL fixes this by providing a desired size for the Drawable to Bitmap conversion. For users that already have an image, there should be no change as the Drawable is already generated from a Bitmap with the same size.

I'm using the same bouncer_user_switcher_icon_size value everywhere now.

Fixes: 419279298
Test: manual
Flag: com.android.systemui.scene_container
Change-Id: I9f3d537410595c1f02f1b2e3b23d3bc944cf2bc4