HLA-935: Update HDRTAB for MVM Products

[s-goldman]

Resolves HLA-935

This PR adds two new header keywords to MVM drizzled (drc/z) products. These include the name (SVMINPUT) and creation date (DATE-SVM) of each of the SVM images included within the MVM. These are inserted into the zeroth extension header for each of the filter-level products. These are listed high up in the header table (as requested) and can be fairly long (see image). The names and location of these keywords can easily be altered.

TODO: I'm still working on some unit tests for this code using unnittest.mock, but the requirement that a file has to be opened has made this challenging. I will likely use the sample_svm files within the test/hap directory.

Checklist for maintainers

• [x] added entry in CHANGELOG.rst within the relevant release section
• [x] updated or added relevant tests
• [x] updated relevant documentation
• [x] added relevant label(s)
• [ ] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 77.77778% with 12 lines in your changes missing coverage. Please review.

Project coverage is 31.75%. Comparing base (6f479ef) to head (84e0ea1).

Files	Patch %	Lines
drizzlepac/haputils/processing_utils.py	70.58%	10 Missing :warning:
drizzlepac/hapmultisequencer.py	0.00%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1796      +/-   ##
==========================================
- Coverage   33.28%   31.75%   -1.53%     
==========================================
  Files         126      160      +34     
  Lines       31164    35184    +4020     
  Branches     5778        0    -5778     
==========================================
+ Hits        10372    11173     +801     
- Misses      19626    24011    +4385     
+ Partials     1166        0    -1166     

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[mdlpstsci]

@s-goldman In case my test branch of this code is wacky, can you please give me access to the output products you generated before and after this code was implemented. I cannot see that you made any change based upon my last comment (which would make sense if I have a wacky branch).