fix parameter cached beetwen elaborations

[Risto97]

Attempt at solving #181

[coveralls]

coverage: 95.065% (+0.004%) from 95.061% when pulling 7eb579f on Risto97:main into 42d877d on SystemRDL:main.

[amykyta3]

This looks like it should work, but I want to take a closer look to see if there's a more correct place to fix this.
I suspect it might be better to suppress copying the cached value in Parameter._copy_for_inst() in parameter.py

[amykyta3]

Yep. Turns out clearing the parameter cache in Parameter._copy_for_inst() works as well, and is a more appropriate place to handle this.

Rejecting this PR, but thank you nonetheless for looking into this!