Too much RAM usage on drc_rosetta.py

[hakan-demirli]

Description

https://github.com/The-OpenROAD-Project/OpenLane/blob/master/scripts/drc_rosetta.py Every one of these functions creates the whole database in RAM and write it back after it is finished. The problem is if the design is huge (more than 100k cells) the RAM consumption increase substantially. Especially tr_to_klayout at its peak use more than 60 GBs of RAM.

Proposal

Rather than saving the conversion object as a variable write each line directly to the file.