Code Quality: Clean up App.Shell

[0x5bfa]

Description

I didn't know what this namespace is for. So I started working on readability refactoring first (stage 2).

2. Rename variables with preferred name to follow the guideline (The most likely to happen is that I rename property-backing-field from '_isHidden' to '_IsHidden')

Motivation & Context

• Improved readability
• Updated variables to be more accurate.

Warning
Please do not review code lines that I did not changed. I cannot make more diff. If there're more codes that are preferred to change, I will do that and mark that PR as the final one for that stage.

PR Checklist

• Were these changes approved in an issue or discussion with the project maintainers? In order to prevent extra work, feature requests and changes to the codebase must be approved before the pull request will be reviewed. This prevents extra work for the contributors and maintainers.
  Related Code Quality: Continued work to clean up entire project #12340
• Did you build the app and test your changes?
• Did you check for accessibility? You can use Accessibility Insights for this.
• Did you remove any strings from the en-us resource file?
  • Did you search the solution to see if the string is still being used?
• Did you implement any design changes to an existing feature?
  • Was this change approved?
• Are there any other steps that were used to validate these changes?

Screenshots

None

[hecksmosis]

LGTM

[ferrariofilippo]

Most comments are about documentation, but overall LGTM
Also, why did you remove the versioning thing?

[0x5bfa]

Thank you! I missed that file and oc I should do split. I'm going to do that later.

Also, why did you remove the versioning thing?

Minimum windows version is earlier than Files.App project minimum windows version. We should add them back when we introduce Uno or something. But for now adding only there is redundant.

PS, All done

[ferrariofilippo]

LGTM

[hecksmosis]

LGTM