tweak the provided pfsDesign just before converging

tweak the pfsDesign/pfsConfig just before converging cobras,

• recalculate target ra and dec with proper motion and parallax.
• recalculate x_mm and y_mm with proper motion, parallax and atmospheric refraction(if available).
• override ra, dec, pfiNominal in pfsConfig.
• converge to pfsConfig.pfiNominal instead of pfsDesign.pfiNominal.

Note that keep the same sha/designId, even if ra and dec has been updated.