Ignore serverComponentChanges in pages (#66312)
## Description
I discovered a bug related to the coexistence of the app router and
pages router in our application. When a page is being served by the
pages router, any changes to server components (in this case,
`globals.css` imported from `app/layout.tsx`) cause the entire page to
reload, significantly lowering productivity.
I believe this is not the intended behavior since server component
changes should have no impact on pages served by the pages router.
## Investigation
I traced the changes and found that:
- At the point of this PR
(https://github.com/vercel/next.js/pull/41464), the process seems to be
handling this correctly.
- Later, in this PR (https://github.com/vercel/next.js/pull/45268), it
started causing reloads, seemingly intended for the app router but
inadvertently affecting the pages router as well.
Given that separate `hot-reloader-client.ts` files are now being used
for the app router and pages router, it is now possible to correctly
branch the hot-reloading process.
I have tested this change locally and it is working fine.
