restore public status of NWBMetaDataEncoder encoder

[h-mayorquin]

This should fix #1141.

I want to do this after #1139 to minimize conflict errors. This PR has #1139 as base.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.68%. Comparing base (64fb9e0) to head (f56bb7d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1142      +/-   ##
==========================================
+ Coverage   90.58%   90.68%   +0.09%     
==========================================
  Files         128      129       +1     
  Lines        8011     8178     +167     
==========================================
+ Hits         7257     7416     +159     
- Misses        754      762       +8     

Flag	Coverage Δ
unittests	90.68% <100.00%> (+0.09%)	⬆️

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Files with missing lines	Coverage Δ
src/neuroconv/basedatainterface.py	95.34% <100.00%> (ø)
...aces/behavior/neuralynx/neuralynx_nvt_interface.py	98.38% <100.00%> (+0.02%)	⬆️
...nv/tools/nwb_helpers/_metadata_and_file_helpers.py	86.57% <100.00%> (-0.09%)	⬇️
...c/neuroconv/tools/testing/data_interface_mixins.py	95.55% <100.00%> (ø)
src/neuroconv/utils/__init__.py	50.00% <ø> (ø)
src/neuroconv/utils/json_schema.py	95.03% <100.00%> (ø)