feat(clerk-js,shared): Remove expired_token retry flow (#8108)

The previous session token is now always sent in the /tokens POST
body (via the `token` param), so the backend no longer needs to
request it via a 422 missing_expired_token error and retry.

Removes:
- MissingExpiredTokenError class and its re-export from @clerk/shared
- The catch-and-retry logic in Session.#createTokenResolver
- 4 related tests in Session.test.ts