Port App Router layouts to Pages Router

[kidlj]

Goals

1. Make Pages Router have the same layout features of App Router.

Non-Goals

No response

Background

The App Router layouts are good to use and make Pages Router layouts seem obsolete. However, not all components library(like @fluentui/react-components) are compatible with Server Side Component, so we still need Pages Router, but also want some App Router features, like the new layout system.

Proposal

Port App Router layout features to Pages Router.