[Nextjs] Move ComponentLibrary from a separate route to Layout.tsx

[addy-pathania]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

Customers typically customize catch-all route and Layout.tsx with various things like React contexts.
That mean they need to re-apply those modification on the DesignLibrary route too, which makes user experience worse.

• Removed component-library/render file route and now redirectd to /
• Renamed ComponentLibraryLayout to DesignLibrary for distinction of Layouts and all related utils and functions.
• All rendering logic has been unified into a single Layout.tsx which now handles the rendering of DesignLibrary based on renderingType

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[stasmaxymov]

I think there are missing changes to editing-render-middleware.ts, as now it should redirect to a root path intead of /component-library/render

[art-alexeyenko]

I left some minor comments for your consideration, and please make sure azure pipeline completes.
Regardles, approved. Good job and well done Addy.