Migrate TabNav component to TSX

[VanAnderson]

This PR migrates the TabNav component to TypeScript as part of the TypeScript refactor.

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The changes in this PR will be included in the next version bump.

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[VanAnderson]

This felt like a weird thing to do - I was trying to parallel some patterns in src/UnderlineNav.tsx and I could not get the props for L19 unless I had an existing Parent element here.

This also seems to be producing some console errors in the tests (though they still pass):

Not sure if the tests needs to be adjusted or if trying to pull out a parent like this is just a bad idea?