Improvements to WLA/RI flow (in advance of adding option for TDWLARI vs sequential WLA + RI)

Prep work to add option for TDWLARI vs sequential WLA + RI as a
simulation flag

gen_design, wla_improved
-Moved capacitance/layer determination into wla_improved
gen_design fully functional with new object io

Updated wla_improved, repeater_insertion, and wla_topdown_with_repeaters
to allow full start to finish runs of gen_design with new IO