Support only latest PyNWB

[CodyCBakerPhD]

As per previous discussion about what range of support NWB Inspector ought to have with past PyNWB/HDMF versions - we decided it should only support latest

This simplifies a lot of conditions on the core inspection logic, individual checks, and what the testing suite is responsible for checking

The only aspect that cannot be replaced is using old versions of PyNWB to generate example files with particular failures that are no longer possible to achieve in latest PyNWB - these are still good to check the inspection logic on since someone could write a file using an older version but inspect it in a different environment (DANDI validate/upload would outright require that) - so I'm keeping those helpers around

[CodyCBakerPhD]

TODO in follow-up: re-implement #265

[stephprince]

Looks good! Added a couple comments/questions.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.

Project coverage is 85.03%. Comparing base (c7861f4) to head (050ddc5).
Report is 3 commits behind head on dev.

Files with missing lines	Patch %	Lines
src/nwbinspector/checks/_images.py	88.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #510      +/-   ##
==========================================
+ Coverage   79.53%   85.03%   +5.50%     
==========================================
  Files          48       48              
  Lines        1412     1390      -22     
==========================================
+ Hits         1123     1182      +59     
+ Misses        289      208      -81     

Files with missing lines	Coverage Δ
src/nwbinspector/_dandi_inspection.py	98.03% <100.00%> (+76.88%)	⬆️
src/nwbinspector/_nwb_inspection.py	85.49% <100.00%> (+6.08%)	⬆️
src/nwbinspector/checks/_images.py	89.47% <88.23%> (-1.44%)	⬇️

... and 3 files with indirect coverage changes