TypeScript typings restored and authentication handling improved

This release restores proper TypeScript typings for sanity/structure, and improves authentication handling for studios configured with auth.loginMethod: 'token' or are embedded in dashboard.

• Fixes an issue causing the studio to freeze if using parentNode as field name.
• sanity@5.3.0 had a regression where structureTool(), presentationTool(), and a few other APIs ended up with any as their type, instead of the rich typescript typings that they’re supposed to have. In this release the types are back 😮‍💨
• Studios configured with auth.loginMethod: 'token' or embedded in Dashboard will now strictly enforce token based authentication and no longer silently fall back to cookie authentication when session cookies exist from other studios on the same domain. Similarly, studios with auth.loginMethod: 'cookie' will now ignore tokens in localStorage.