Reader: Convert SiteStream to functional component and add sidebar

[creativecoder]

Proposed Changes

• Converts SiteStream to a functional component
• Adds sidebar with post count, follower count, and most used post tags
• Moves common components and functions for access by both FeedStream and SiteStream

This PR replicates the changes from #78702 and #78706 done for the FeedStream component.

Testing Instructions

• Visit /reads/blogs/{blog-id} to see the sidebar added.

Before	After

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-72217

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-72217&env=jetpack

[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

App Entrypoints (~35 bytes added 📈 [gzipped])

name                   parsed_size           gzip_size
entry-stepper               +145 B  (+0.0%)      +34 B  (+0.0%)
entry-main                  +145 B  (+0.0%)      +39 B  (+0.0%)
entry-login                 +145 B  (+0.0%)      +38 B  (+0.0%)
entry-subscriptions         +126 B  (+0.0%)      +34 B  (+0.0%)
entry-domains-landing       +126 B  (+0.0%)      +34 B  (+0.0%)
entry-browsehappy           +126 B  (+0.1%)      +34 B  (+0.1%)

Common code that is always downloaded and parsed every time the app is loaded, no matter which route is used.

Sections (~305 bytes added 📈 [gzipped])

name                  parsed_size           gzip_size
reader                    +1077 B  (+0.1%)     +305 B  (+0.1%)
write-flow                 +605 B  (+0.1%)     +193 B  (+0.1%)
videopress-flow            +605 B  (+0.1%)     +193 B  (+0.1%)
link-in-bio-tld-flow       +605 B  (+0.1%)     +193 B  (+0.1%)
free-flow                  +605 B  (+0.1%)     +193 B  (+0.1%)
build-flow                 +605 B  (+0.1%)     +193 B  (+0.1%)

Sections contain code specific for a given set of routes. Is downloaded and parsed only when a particular route is navigated to.

Async-loaded Components (~2058 bytes removed 📉 [gzipped])

name                                                 parsed_size            gzip_size
async-load-calypso-reader-site-stream                    +4418 B  (+31.1%)    +1796 B  (+40.1%)
async-load-design-blocks                                  +831 B   (+0.0%)     +267 B   (+0.0%)
async-load-calypso-reader-feed-stream                     +736 B   (+4.0%)     +766 B  (+13.6%)
async-load-calypso-components-web-preview-component       +605 B   (+0.1%)     +193 B   (+0.1%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[davemart-in]

Looking good! Nicely done.

[creativecoder]

Note that I'm going to merge in #78853 to this branch, to remove the need for an additional deploy.