Analytics settings offers a new account when the account list fails

## Bug Description

When the Analytics account list fails to load, the settings screen shows an error line. Under the error, the screen shows the create account form, filled in with the site's details and ending with **Create Account**.

Any failure of the account list causes this: an outage at Google, a rate limit, an expired grant, or a lost connection.

The screen must say the account list failed to load, and offer a button to try again, with the account fields kept.

## Steps to reproduce

1. In Site Kit, go to **Settings > Connected Services > Analytics** and click **Edit**.
2. With Tweak (browser extension), set a `500` response for `.*analytics-4/data/account-summaries.*`, with `{"code":"internal_server_error","message":"Something went wrong.","data":{"status":500}}` as the response payload.
3. Reload the page.

## Screenshots

## Additional Context

- Plugin Version: 1.185.0
- Asana Task: https://app.asana.com/1/8468971550303/project/1217014300014478/task/1217252529664988

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## Acceptance criteria

*

## Implementation Brief

* [ ]

### Test Coverage

*

## QA Brief

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## Changelog entry

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Start in Site Kit's Settings > Connected Services > Analytics > Edit flow and reproduce the failure by returning a 500 response for the analytics-4/data/account-summaries endpoint. Trace the account-list error state and verify that it explains the loading failure, offers a retry button, and preserves the account fields instead of showing Create Account.

Written by the indexing model from the issue text.