Introduce pfsDesign/Config validation code

As reported on slack:

https://sumire-pfs.slack.com/archives/C9TDPMVHT/p1671252144208469

 A number of targets in pfsDesign 0x031107ae86f9db65 have unrealistic PFI positions, in that for each target the distance from the cobra center is greater than the L1+L2 arm lengths.

To avoid such situations happening in the future, I propose introducing a pfs_utils utility that validates the contents of a given pfsDesign. This utility would include at least a check for the PFI target positions.