Allow users to disable fix_notebook to check/resolve kernel validity

[ClaytonAstrom]

Problem

fix_notebook can be very heavy handed for kernel resolution. If a user wanted to customize the kernel matching logic, they would have to fork voila to achieve any customization in this regard. While I agree it's good to have some guard rail in, users should be able to disable this logic in favor of handling it within their own kernel manager

Proposed Solution

Add a toggle that can disable this logic