feat: add option to ignore locked fields

[ReenigneArcher]

Description

This PR adds an option to completely ignore locked fields when adding themes or collection metadata.

Screenshot

Issues Fixed or Closed

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update (updates to dependencies)
• Documentation update (changes to documentation)
• Repository update (changes to repository files, e.g. .github/...)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated the in code docstring/documentation-blocks for new or existing methods/components

Branch Updates

LizardByte requires that branches be up-to-date before merging. This means that after any PR is merged, this branch
must be updated before it can be merged. You must also
Allow edits from maintainers.

• I want maintainers to keep my branch updated

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (5e4da42) 70.10% compared to head (b2921d7) 70.10%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #347   +/-   ##
=======================================
  Coverage   70.10%   70.10%           
=======================================
  Files          12       12           
  Lines        1007     1007           
=======================================
  Hits          706      706           
  Misses        301      301           

Flag	Coverage Δ
Linux	70.10% <33.33%> (ø)
Windows	69.91% <33.33%> (ø)
macOS	69.91% <33.33%> (ø)

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

Files	Coverage Δ
Contents/Code/default_prefs.py	100.00% <ø> (ø)
Contents/Code/plex_api_helper.py	49.49% <33.33%> (ø)