Make the codebase more PDK-agnostic by moving tech-specific code to `tech.py` and tech specific files (e.g. def files, tile_sizes.yaml) to `tech/<pdkname>` subdirectory.
When set, it configures all user projects with `pg_vdd: false`. This is for ihp0p2 shuttle, which doesn't have power gating yet (tt-multiplexer defaults to enable the pg when `pg_vdd` is not explicitly specified).