Inline board configuration call into printvars call

This is so that:
 - It's consistent with product configuration
 - The return type of board/product config's main functions
   and the arguments to printvars can be changed without
   also making a change in the soong repository. (what I'm about
   to do)
 - Removes obsolete TODO

Bug: 221312856
Test: Presubmits
Change-Id: I593f180881eab9521012df202af8f0233bc0b6ae