[flexiglass] UX polish for bouncer scene: PIN and Pattern

Really brings the UI into spec, especially regarding sizing and spacing
of various elements.

Does so for PIN and Pattern, a little for password - but that requires
more work.

Fix: 300677757
Bug: 282730134
Bug: 281871687
Test: screenshot tests in companion vendor CL
Test: manually verified inner, outer, landscape/portrait,
unfolded/half-foded on foldable hardware
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT

Change-Id: I1aa5e3e63d888bad0e63c07425f2a2a2f723f761