[DocsUI M3] Add measurement system tokens

These tokens are replicated from the Android UX Design System,
adding them in the code to make sure we are speaking the same
language for spacing with UX.

Bug: 379184264
Test: m DocumentsUIGoogle
Flag: com.android.documentsui.flags.use_material3
Change-Id: I793b78904bd24bd683bf9a14f80d30ccec8b637d