[New CDot Nav] Use portal-vue to add alert to top of page
Problem
Currently, any error alerts for the billing account settings page that are rendered by Vue components will show up half-way down the page, under the payment methods table. This is because the payment methods table is rendered in Rails before the Vue app is rendered.
Proposal
Similar to the implementation in [New CDot Nav] Migrate sidebar to use portal (#7227), use portal-vue
to render the alert at the top of the page above the payment methods table.
Based on other Figma alert example, render alert below page header. Confirm with UX during code review.
Edited by Laura Callahan