[DocsUI M3] No literal dimension numbers in the code

Dimension related view setters like setStrokeWidth are only
dealing with pixel numbers, not dp numbers, so we shouldn't
use any number literal in the code. Instead, we should define
the dimension as a number resource and use getDimensionPixelSize()
to get its pixel value in the code before calling these setter
methods.

Bug: 402617801
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: Ifbbfd2b006985841ff9a581a485e924d1bf1976b