fix interception routes with dynamic segments (#59273)
### What?
Using an interception marker next to a dynamic segment does not behave
properly when deployed to Vercel
### Why?
The named route regex that gets created is not accounting for the
interception marker, which is causing the non-intercepted route to match
the intercepted serverless function.
### How?
This factors in the interception marker when building the named route
regex so that the non-intercepted route regex properly matches when
loading the non-intercepted page.
Deployment verified here: https://test-intercept-mu.vercel.app/
Closes NEXT-1786
Fixes #54650
