Use bluesky-darkframes

[mrakitin]

We need to convert the prototype of the code which inspired the bluesky-darkframes library to actually use it:

• code: https://github.com/bluesky/bluesky-darkframes
• docs: https://blueskyproject.io/bluesky-darkframes/
• example: Darkframes NSLS-II-CSX/profile_collection#32

[mrakitin]

May need @danielballan's support for that. We discussed using it with @elistavitski and @lcdesilva today during a call, and agreed it should be a long-term solution replacing the upcoming open/close run changes in https://github.com/NSLS-II-QAS/profile_collection/blob/pe_tests_local/startup/83-pe-plans-local.py once we are allowed onsite and have a beam to test the dark frames subtraction with photons.

[jklynch]

I worked on this with Chanaka. We did get bluesky-darkframes integrated but decided to stay with the code Chanaka has already written, just move it to an ophyd class so it works with count. This is a good opportunity for me and Chanaka to learn to write an ophyd class.