Improve acquire/guide using SCAM

[chazshapiro]

Not sure when we'll get to this, but I wanted to log these notes on implementation:

Record some shape info for databases

"Phase 2 acquisition" — only for coordinate-ful acquire, not "acquire here"

Get virtual slit location from FPoffsets/FITS headers, wherever
Identify which SCAM the virtual slit is on

Go into control loop using SCAM images
Cut out postage stamp around the virtual bullseye — PARAMETER: stamp size ~ 4
Compute weighted centroid — PARAMETER: weight FWHM ~ 2" (conservative seeing)
Compute weighted 2nd moments

How to do loop - update the ACAM GOAL until centroid is on bullseye or fully switch to SCAM guiding? Need to update ACAM goal at the end at least

Once target is on bullseye, switch back to usual ACAM guide loop

[astronomerdave]

Started a branch for this work with PR #363