Eliminate requirement of @react-router/remix-routes-option-adapter package

[mikkpokk]

Currently, it converts the routes object to the RR7 format using a Promise function.

We can clean up our routes object tree and eliminate the need for an adapter. However, this will entirely remove Remix support and must be released as a major version update, considering the impact on Remix users.

Useful resources for migration:
@react-router/remix-routes-option-adapter
@react-router/fs-routes