fix(react): update radio button group state initialization

[joshblack]

Closes #9041

This updates how we initialize our selected state value from a || expression to a ternary that checks if the value is undefined. When using ||, the state would be incorrectly initialized if the value was false-y but not undefined (like the value 0).

I also took this small change to convert some of the tests for RadioButtonGroup to RTL. It also updates the jest-dom matchers to be brought in automatically.

Changelog

New

Changed

• Update RadioButtonGroup.js to correctly initialize selected state
• Update RadioButtonGroup-test.js file to start using RTL
• Update jest-config-carbon to automatically bring in jest-dom matchers

Removed

Testing / Reviewing

• Review the test case and make sure it mirrors the one brought up in RadioButtonGroup mishandles the input falsy value as an undefined value #9041
• Verify test passes
• Verify component continues to work in Storybook

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[tw15egan]

LGTM 👍 ✅