fix(CallToAction): update and constrain prop object type shape

[TylerAPfledderer]

Description

This PR primarily addresses a React console warning from the CallToAction hero component:

Warning: CallToAction: `key` is not a prop. Trying to access it will result in `undefined` being returned. If you need to access the same value within the child component, you should pass it as a different prop.

Trying to use the key prop will only result in receiving undefined and create styling bugs when using it to render the button variant. Instead create unique prop index to access an index value for use in the props logic.

Also modifies typing related CallToAction so that:

• Usage of the Button component props variant and isSecondary are constrained to only the logic within CallToAction to determine their values per instance
• When creating data for the buttons in a hero component the user is not required to explicitly supply an index value when that is provided via render mapping.

Related Issue

N/A

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[wackerow]

Lgtm, thanks @TylerAPfledderer!