fix(Checkbox): add positioning to checkbox input for native validation alignment

[jnm2377]

Closes #10002

Changelog

• even thought checkbox input isn't visible, this aligns it to the visible checkbox so that native browser validation will be aligned
• add validation example on checkbox stories (can remove this once approved)

Testing / Reviewing

View React deploy preview:

1. go to checkbox validation story
2. don't check the box
3. click the button
4. browser validation should align below checkbox

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