fix: flipper icon and menu item text in high contrast mode

[khamudom]

Description

Added color to the host selector in menu-item to fix high contrast white. Updated the high contrast selector in the flipper style to be set on a class instead of the attribute.

menu-item
before

after

flipper
before




after

Motivation & context

Issue type checklist

• Chore: A change that does not impact distributed packages.
• Bug fix: A change that fixes an issue, link to the issue above.
• New feature: A change that adds functionality.

Is this a breaking change?

• This change causes current functionality to break.

Adding or modifying component(s) in @microsoft/fast-components checklist

• I have added a new component
• I have modified an existing component
• I have updated the definition file
• I have updated the configuration file

Process & policy checklist

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

[EisenbergEffect]

I thought we were trying to base things off of attribute rather than class, for reasons of integration with React and such. Can someone clarify?