Implement the People UI in Compose (1/2)

This CL implements the People UI using Jetpack Compose. Note that this
implementation won't be used by SystemUI yet, and can only be viewed
using the SystemUIGallery app at the moment.

Once ag/19500380 is submitted (blocked by b/236146570), the screenshot
tests will use the Compose implementation. You can see the visual
difference between the implementations in ag/19498514. As explained in
b/238993727#comment10 the result is slightly different (and improved
over the current View implementation).

Note that the fake values of this screen have been moved from the
current PeopleSpaceScreenshotTest, and are now reused there as well (see
ag/19568794).

Bug: 238993727
Test: atest SystemUIGoogleScreenshotTests
Change-Id: I4d2f241ccf768ef3fccc01ce196418ce7fc26492