ENH: add support for passing field keys for colors and linewidth in streamline plot annotations

[neutrinoceros]

PR Summary

Closes #4454, incidentally fix a couple small issues with StreamlineCallback's implementation.

demo:

import yt

ds = yt.load("IsolatedGalaxy/galaxy0030/galaxy0030")
p = yt.ProjectionPlot(ds, "z", ("gas", "density"))
p.annotate_streamlines(
    ("gas", "velocity_x"),
    ("gas", "velocity_y"),
    linewidth=("gas", "velocity_z"),
    linewidth_upscaling=3,
    color=("gas", "velocity_magnitude"),
    cmap="turbo",
)
p.zoom(20)
p.save("/tmp/")

PR Checklist

• write error and deprecation messages
• extra validation of input types (in particular, check consistency with MPL)
• New features are documented, with docstrings and narrative docs
• Adds a test for any bugs fixed. Adds tests for new features.

[matthewturk]

like it!

[neutrinoceros]

had an insignificant conflict, fixed it

[neutrinoceros]

@matthewturk if you're still up for it, this is now ready to go

[matthewturk]

I actually thought I'd already approved!

[neutrinoceros]

you did, I just 'dismissed' your approval when I fixed a conflict !