custom parameter formatting from_updk function

[Dam-masse]

Is your feature request related to a problem? Please describe.
In the current implementation of the from_updk function the parameters string is passed with a fixed format that makes it compatible with only certain software for the PCell replacement.

Discussed also in PR" fix to the output of the from_updk function #2645"

Describe the solution you'd like
from_pdk should accept as imput a string that describes the formatting required in the blakcboxes.

[joamatab]

We could pass a function or support both styles of upkd naming ('=', ':')

#2645

we can also fix the list with one value serialization issue
#2750

@sebastian-goeldi