Performance issues addressed, 1st patch

[klayoutmatthias]

Addresses #1

• [X] Tests pass (as far as compatibility with main/klayout 0.27.12 is concerned, tests formally do not pass, but no new errors)
• [ ] Appropriate changes to README are included in PR

Description/reasoning: see length explanation of the changes + important hints in the commit message of https://github.com/efabless/globalfoundries-pdk-libs-gf180mcu_fd_pr/commit/b434aedd6679eadabf252331834e6251106ae367