Hsi read data flexible hdr format

[HaleySchuhl]

Describe your changes
Update to /plantcv/hyperspectral/read_data.py with end goal of expanding flexibility with image formats. Moves .hdr file parsing and dictionary creation into a helper function.

Type of update
Is this a:

• New feature or feature enhancement
• Work in progress

Associated issues

• New .hdr format for HSI images #930

Additional context
Add any other context about the problem here.

For the reviewer
See this page for instructions on how to review the pull request.

• PR functionality reviewed in a Jupyter Notebook
• All tests pass
• Test coverage remains 100%
• Documentation tested
• New documentation pages added to plantcv/mkdocs.yml
• Changes to function input/output signatures added to updating.md
• Code reviewed
• PR approved

[codecov]

Codecov Report

Merging #956 (a4edfcb) into main (9dbf801) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #956   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          141       141           
  Lines         6003      6028   +25     
=========================================
+ Hits          6003      6028   +25     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
plantcv/plantcv/hyperspectral/__init__.py	100.00% <100.00%> (ø)
plantcv/plantcv/hyperspectral/read_data.py	100.00% <100.00%> (ø)
plantcv/plantcv/readimage.py	100.00% <100.00%> (ø)