Update per-layer resistance with the results from segment-based regression across PDKs

### Description

The current values are wrong - there's probably something off with the net-based regression which caused the resistance fit to not be linear when it should.

PDKs:
 - [x] asap7
 - [ ] gf12
 - [x] gf180
 - [x] ihp
 - [x] nangate45
 - [ ] sky130hd
 - [x] sky130hs
