Script for new PDK tech def creation to copy symbols from reference BAG_prim

[martinjankoehler]

New PDK tech defs repos are always copied from cds_ff_mpt-bag3 as a reference.

After creating the schematic views using load("prim_pcell.il"),
the missing symbol views should be created
as described in https://bag3-readthedocs.readthedocs.io/en/latest/new_pdk_setup.html

"Create the symbols for each generated pCell using the recommended template in the BAG_prim library for cds_ff_mpt."

This commit adds a script intended to do exactly this, so i.e.:

$> ./copy_symbols.py --ref $BAG3_CDS_FF_MPT/OA/BAG_prim --dest $BAG3_MY_PDK/OA/BAG_prim