Remove CxoTime custom fast parser, use astropy built-in

[taldcroft]

Description

The CxoTime fast C parser was the prototype for astropy. That fast parser is now built in to astropy so there is no need for the custom version in cxotime.

Interface impacts

None

Testing

Unit tests

• Mac

Independent check of unit tests by Jean

• Linux
• Mac

Functional tests

In the local unit test, I did git clean -fxd to ensure no lingering binary files were accidentally allowing things to work.

[jeanconn]

This makes sense and seems fine. I note that I'm not immediately lear on how to initialize the astropy time classes, as the docstring doesn't seem to address the items in the init signature. But that's not a cxotime issue.

Init signature:
TimeYearDayTime(
    val1,
    val2,
    scale,
    precision,
    in_subfmt,
    out_subfmt,
    from_jd=False,
)
Docstring:     
Year, day-of-year and time as "YYYY:DOY:HH:MM:SS.sss...".
The day-of-year (DOY) goes from 001 to 365 (366 in leap years).
For example, 2000:001:00:00:00.000 is midnight on January 1, 2000.

The allowed subformats are:

- 'date_hms': date + hours, mins, secs (and optional fractional secs)
- 'date_hm': date + hours, mins
- 'date': date

[taldcroft]

These TimeFormat subclasses are defining a contained object within the Time class which is not directly set by the user. The Time class is defined in astropy/time/core.py.

[jeanconn]

This looks good and makes sense to me. One issue is that it is difficult to see if the astropy built-in is in any way different from the custom fast parser. I think that just means we should keep an eye on the integration tests in this case.