[Vue] "Back to" callbacks not overridable in other components other than sign-in

### On which framework/platform would you like to see this feature implemented?

Vue

### Which UI component is this feature-request for?

Authenticator

### Please describe your feature-request in detail.

In the sign-in component the link to go to the password reset in included in the footer slot. This gives the ability to override is with custom elements. However all the other components like reset-password or verify-user have the "back to" component hard coded in the template without a possibility to override (besides rendering the complete component yourself).

### Please describe a solution you'd like.

In my opinion there are two options:

1. Introduce new slots to override these part of the templates
2. Re-use the reset-password-footer/verify-user-footer (and other components) and place the "back-to" callback in that footer

I think option 2 is the most viable option, the generic footer slot is used for the entire Authenticator component so the specific footer slots in the component can be used for the "back-to" callback.

I am willing to submit a PR for the Vue package, if there is a good option this will be merged.

**components/reset-password.vue**
https://github.com/aws-amplify/amplify-ui/blob/main/packages/vue/src/components/reset-password.vue#L119

_As you can see here, an empty slot and no specific option to override the "back-to" button_

**components/sign-in.vue**
https://github.com/aws-amplify/amplify-ui/blob/main/packages/vue/src/components/sign-in.vue#L143

_As you can see here, the footer slot is used for the "back-to" button_

I don't know if you consider this a Breaking Change is the slot is used? I can't imagine the footer slot in sub components is often used for other things.

Let me know if you would like for me to submit a PR.

### We love contributors! Is this something you'd be interested in working on?

- [X] 👋 I may be able to implement this feature request.
- [ ] ⚠️ This feature might incur a breaking change.

Start with packages/vue/src/components/reset-password.vue around the referenced template and compare it with packages/vue/src/components/sign-in.vue, especially their footer slots. Review the corresponding verify-user component as well, then choose a consistent slot or footer approach so the other Authenticator components expose an overridable “back to” callback without requiring complete custom rendering.

Written by the indexing model from the issue text.