Update app handle to match the UI spec

Makes the rounding at the ends of the app handle semicircular.
Centers the handle vertically on the status bar.

UI spec: https://www.figma.com/design/flC1tPqknJnIVa8m5fhUQv/App-Headers-%26-Menus-(V)?node-id=7880-36203

Bug: 343720907
Flag: com.android.window.flags.enable_desktop_windowing_mode
Test: manual
Change-Id: I0ed3d3bee1f04a4afcc0bfbaa6253117acce4333