Update MultiSpec schema to provide keywords for recording extraction characteristics

[jemorrison]

Partially resolves JP-3169

Is needed to close spacetelescope/jwst#7773

This PR updates the MultiSpec model to include the xstart, xstop, ystart, ystop values (if they are defined) so they can be recorded in the FITS header

The extraction x center and y center were already defined with keyword values of EXTR_X, EXTR_Y.
Since the extraction locations are related to these values I picked
EXTRXSTR: x start of extraction region
EXTRXSTP: x stop of extraction region
EXTRYSTR: y start of extraction region
EXTRYSTP: y stop of extraction region

But these value can be changed if a better set can be found

Checklist

• added entry in CHANGES.rst (either in Bug Fixes or Changes to API)
• updated relevant tests
• updated relevant documentation
• updated relevant milestone(s)
• added relevant label(s)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.87%. Comparing base (4d7c3a6) to head (bb886a7).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #264      +/-   ##
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+ Coverage   64.84%   64.87%   +0.03%     
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  Files         103      104       +1     
  Lines        5694     5699       +5     
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+ Hits         3692     3697       +5     
  Misses       2002     2002              

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[jemorrison]

@hbushouse @tapastro I could not add you to the list of reviewers. Are the names of the FITS Keywords for these parameters ok to you. This PR will need to be merged before the extract 1d code updates will be able to use them

[hbushouse]

We already have a couple of similar sets of keywords that give region limits:

SUBSTRT1, SUBSTRT2, SUBSIZE1, SUBSIZE2 - which record the location and size of subarrays relative to the full detector
SLTSTRT1, SLTSTRT2, SLTSIZE1, SLTSIZE2 - which record the location and size of 2-D cutouts performed in extract_2d

These work a bit differently, in that instead of including explicit start/stop values, they only specify the start location and then record the size.

So if we want keywords that record start/stop values, we can't just duplicate these existing sets by simply changing the prefix (i.e. use "EXTR" instead of "SUB" and "SLT"). But I'm wondering if we should at least conform to the same use of axis numbers in the keywords, instead of using "x" and "y"? Unfortunately we already have a precedent set with the "EXTR_X" and "EXTR_Y" keywords that are used to record the center of the circular apertures used to make 1-D extractions from IFU cubes. So ... not sure what the best naming convention should be for these new keywords.

Not a big fan of the fact that "EXTRXSTR" and "EXTRXSTP" are so similar looking until you see the difference in the very last letter. But I honestly don't have many better suggestions. So I guess, after all of this, I'm OK with the proposed keyword names.

[hbushouse]

Needs a change log entry