Fix accessibility prop name inconsistencies

[redallen]

Property names for aria attributes are inconsistent. Some examples:

• AboutModalContainer takes the following properties: ariaLabelledbyId, ariaDescribedById. Note inconsistencies in by vs By.
• AboutModalBox takes the raw HTML properties: aria-labelledby, aria-describedby
• Alert takes variant and variantLabel and sets aria-label=undefined as a default property without it being an actual component property that we can typecheck.
• I'm sure there's more...

Codebase names:

• ariaLabel: 148
• aria-label: 424
• aria-controls: 10
• ariaControls: 3
• aria-labelledby: 74
• ariaLabelledbyId: 10
• aria-describedby: 18
• ariaDescribedById: 12
• variant: 694
• variantLabel: 13
• There's more... See the aria property list and use a global regex tool to spot our naming inconsistencies.

We are already mostly using the HTML properties, so I propose we introduce a breaking change to rename properties like ariaLabelledbyId to their HTML counterpart aria-labelledby. If we need to do logic with them in the component, we can rename them to camel-case in the property destructuring that already takes place using the : syntax:

{
  'variant-label': variantLabel,
  'aria-label': ariaLabel,
  'aria-labelledby': ariaLabeledBy,
  'aria-describedby': ariaDescribedBy
}

[redallen]

Ref #1525