feat(inject): tasks for injecting catalogs into visibility data

[ssiegelx]

Introduces the FluxCatalog and SpectroscopicCatalog tasks,
which generate synthetic visibilities from a catalog of sources.
Also introduces versions of these tasks that modulate the signal
from each source by a beam model, either an external model, or
one implemented via the beam method of the provided telescope object.

Introduces code for perturbing the redshifts of the eBOSS tracers.

[ssiegelx]

This is a stand-alone module that I have been using to synthesize visibilities for catalogs of point sources. This capability is used in a few places:

• Solving for the beam model by fitting hybrid visibilities from intercylinder baselines to point source models of the sky
• Predicting the signal to noise of the eBOSS stacks by injecting into CHIME data
• Characterizing the transfer function of the stacking pipeline

I've placed it in ch_pipeline rather than draco because it requires the ch_util.fluxcat module.

It also contains functions for perturbing the redshift of sources using the velocity error distributions for the eBOSS tracers (described here: https://github.com/chime-experiment/Stacking/issues/14). We may want to move those functions to a module in draco.util, either tools or something new, since we will need to perturb the redshifts elsewhere.