### What
Fix a bug introduced in #65694 , use app-page runtime for app router
layers
### Why
This is basically reverted the route context picking up logic we had
before.
During the test we found the error thrown
> Module not found: shared-runtime module router-context cannot be used
in rsc layer
Which is caused by a `next/router` imports in rsc page. Decided to
revert to what it was before as the most safe way to load share module
contexts.
It's caused by `next-contentlayer` usage that they're using
`next/router` in server component MDX, but we cannot lint error that
from node_modules. (We actually can, but disabled that due to various
mis-usage of server/client hooks we had before)
Jiachi Liu