Swap usages of colorPrimaryDark on wear to colorSurface

This is done since:
  * colorPrimaryDark and colorPrimary are the same Theme.DeviceDefault
    on phone, so this aligns us with that
  * colorPrimaryDark is normally with status bar/action bar, which are
    not relevant on Wear
  * colorSurface/colorSurfaceVariant more appropriate for the particular
    framework components on Wear that were previously using
    colorPrimaryDark

Bug: 268542165
Test: manually verify watch UI using colorPrimaryDark
Change-Id: I37709a0725a683ffbc068a96a99751f3f7fa5114