[Admin] New admin user edit page

[MadelineCollier]

Summary

This PR is for issue: #5824

This migrates the users/:id/edit page to the new admin. It still relies on the old backend admin controller for the #update action as well as the other top level user tabs such as address, order history, and so on.

In the next couple PRs I will migrate the remaining tabs to the new interface, but for now I thought it best to keep the old interface for actions such as creating a new user, which we definitely want to still have working.

This PR does not handle the issue of permission dependent interface elements. In the old admin, some buttons would not be visible if the user lacked the permissions to action them. However it looks like that is currently standard for the entirety of the new admin as I don't see any permissions checks or anything like this anywhere in the new admin:

      <% if can?(:addresses, @user) %>
        <li class="<%= 'active' if current == :address %>">
          <%= link_to t("spree.admin.user.addresses"), spree.addresses_admin_user_path(@user) %>
        </li>
      <% end %>

If we are using a new helper or gem to manage this and I am just missing something definitely let me know which implementation I can reference! Otherwise for now I will put this up as is because handling if can? permissions checks across the whole of the admin is a bit out of scope for this PR.

In the next PRs I will migrate the other tabs of the user admin (address, order history etc) and will add the modal for user creation (although I may leave the user creation backend logic as is for now as it looks like the issue specifically states that the user invitation flow should be considered a separate task.

Again there weren't really designs for this so I just went for it and tried to keep to our existing components as much as possible. Hopefully it looks decent!

The attached video shows the functionality visually:

Screen.Recording.2024-09-18.at.9.29.12.PM.mov

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[MadelineCollier]

Looks like the promotions spec failures are consistent across all branches and unrelated to this PR

[Promotions GET #show when non admin should be unauthorized](https://app.circleci.com/pipelines/github/solidusio/solidus/6641/workflows/1a2097d4-4450-4d5e-974c-ceb2d39f7258/jobs/61557/tests#failed-test-0)
[Promotions GET #show when admin when finding by a promotion behaves like a JSON response should return JSON](https://app.circleci.com/pipelines/github/solidusio/solidus/6641/workflows/1a2097d4-4450-4d5e-974c-ceb2d39f7258/jobs/61557/tests#failed-test-1)
[Promotions GET #show when admin when finding by a promotion behaves like a JSON response should be ok](https://app.circleci.com/pipelines/github/solidusio/solidus/6641/workflows/1a2097d4-4450-4d5e-974c-ceb2d39f7258/jobs/61557/tests#failed-test-2)