Fix Segmented control's container VisualState adjustment and arrow key focus issues

[Avid29]

Fixes #813 and #814

PR Type

What kind of change does this PR introduce?

Bugfix

What is the current behavior?

1. A SegmentedItem container's VisualState will not be updated until the parent Segmented control's Orientation property is updated. This results in the selected indicator showing incorrectly when items are added.

2. Left/Right arrow keys are inverted in RTL and Up/Down keys aren't handled

What is the new behavior?

1. SegmentedItem containers are updated to match the Segmented control's VisualState when preparing the container for items.

2. Left/Right arrow keys adjust the index properly and Up/Down keys are explicitly handled

PR Checklist

Please check if your PR fulfills the following requirements:

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• Tested code with current supported SDKs(https://github.com/CommunityToolkit/WindowsCommunityToolkit-design-assets)
• Tests for the changes have been added (if applicable)
• Header has been added to all new source files
• Contains NO breaking changes

Other information

[Arlodotexe]

Great improvements! I don't see any logical differences between the old code and the new, except for the fixes and cleanup. Approved 🚀