radio-button: support Windows High Contrast - black theme

[kittenish]

Bug

Demo and steps to reproduce the issue

This blank StackBlitz demo can be used to create a reproduction that demonstrates your issue.

Demo URL (required)*: https://material.angularjs.org/HEAD/demo/radioButton

Detailed Reproduction Steps

1. Enable Windows High Contrast - Black theme
2. Navigate to a radio group using keyboard tab key
3. Observe the focus indicator is not visible
4. Select a radio button with arrow keys or mouse
5. Observe the selected state is not conveyed visually for the user

Explain the expected behavior

In step 3, focus indicator should be visible.
In step 5, selection should be visible.

Explain the current behavior

Focus indicator and selection are not visible.

Discuss the use-case or motivation for changing the existing behavior

It will be difficult to use under Windows high contrast if neither focus nor selection is visible.

List the affected versions of AngularJS, Material, OS, and browsers

• AngularJS: 1..8.0
• AngularJS Material: 1.1.24
• OS: Windows 10 Enterprise (64-bit)
• Browsers: Firefox 79.0.b6

Screenshots

A screenshot on Windows with high contrast mode: