Add new features for extension, allowing one program to depend on another

[schlafly]

This PR makes a few changes needed to support the DESI extension.

The most important algorithmic change is adding a new config file feature, where a program can be marked as depending on another program, via the following:

programs:
    dark1b:
        depends_on: dark

The intention here is to force the NTS to delay giving out any dark1b tiles until all overlapping dark tiles have been observed.

There are a variety of other minor changes.

• Extending the stop date for the default ephemerides out to the end of 2029, to accommodate observing farther into the future.
• new colors for the bright1b and dark1b programs for plotting
• new arguments to make it easier to change the stop date for optimizing hour angles.
• updates to surveymovie to enable it to make movies for the extension program
• deletion of some orphan code I stumbled upon.

Survey simulations with this code are here:
https://data.desi.lbl.gov/desi/users/schlafly/surveysim-20240927/

I think that's all that is needed to do the extension program on the desisurvey/NTS side. I originally intended to also extend the tile file to allow programs to be observed in different types of conditions, but did not actually do that as part of this PR. There is currently a program-to-conditions mapping in the config file, so we won't need to update the tile file to accommodate, but we will need to do some more thinking about how we would want the program selection to look like if we did define a bitmask. We don't need that for the extension and so I've tabled it for now.

[coveralls]

coverage: 30.523% (+0.1%) from 30.403%
when pulling 3c8e52c on extension
into d97b77b on main.