[Toast] Deprecate error prop in favour of tone+leadingIcon prop.

[lone-star]

Feature request summary

We must remove the error prop from the Toast component. The error styling will be achievable by using new props that are being introduced to the Toast component: tone and leadingIcon.

Rationale

Currently the error property in the toast component will activate the styling of the Toast for errors. With the introduction of additional styles (such as magic), we need a more generic way to specify custom colour schemes. Since the tone style is being introduced across Polaris, we will should migrate the Toast component from a dedicated property to using the tone style.

This first PR introduces the magic styles to the Toast component: #11431 as well as the base props.

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Work to be done:

1. Add the tone and leadingIcon props to the Toast component: [Toast] Add tone, actionOnComponent and leadingIcon props to Toast #11431
2. Add error styles to the tone prop and migrate all error usages to tone+leadingIcon. Mark the error prop as deprecated.
3. Remove the error prop in v13

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