JP-1875: Make _get_wcs_values_from_siaf function public for JSDP use

[tapastro]

Resolves JP-1875
Resolves #5663

Also changed _EngDB_Value to EngDB_Value, per ticket comment request.

[codecov]

Codecov Report

Merging #5669 (7344aa8) into master (672c983) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #5669   +/-   ##
=======================================
  Coverage   74.34%   74.34%           
=======================================
  Files         416      416           
  Lines       38110    38110           
  Branches     5000     5000           
=======================================
  Hits        28333    28333           
  Misses       9777     9777           

Flag	Coverage Δ		*Carryforward flag
nightly	75.88% <100.00%> (ø)		Carriedforward from 672c983
unit	54.17% <100.00%> (ø)

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
jwst/lib/engdb_tools.py	100.00% <100.00%> (ø)
jwst/lib/set_telescope_pointing.py	89.45% <100.00%> (ø)

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[hbushouse]

LGTM. Just needs a change log entry.