Clarity improvement in magnifier naming

[Boumtchack]

Link to issue number:

Closes #20126

Summary of the issue:

At the moment, the magnifier module lacks clarity in naming, it uses several terms to talk about the same things and that can lead to confusions

Description of user facing changes:

Users will have a better and clearer desciption and settings of the magnifier

Description of developer facing changes:

Variables and naming will be more consistent and logical

Description of development approach:

Adapting code naming to the User guide terms

Testing strategy:

Known issues with pull request:

Code Review Checklist:

• Documentation:
  • Change log entry
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• API is compatible with existing add-ons.
• Security precautions taken.

[Boumtchack]

@CyrilleB79 I started rewritting the user docs and I'll do the same in the settings when #19913 is closed.