[DevTools] Remove renderer.js from extension build (#26234)

## Summary

When looking into the compiled code of `installHook.js` of the extension
build, I noticed that it actually includes the large `attach` function
(from renderer.js). I don't think it was expected.
This is because `hook.js` imports from `backend/console.js` which
imports from `backend/renderer.js` for `getInternalReactConstants`
A straightforward way is to extract function
`getInternalReactConstants`. However, I think it's more simplified to
just merge these two files and save the 361K renderer.js from the
extension build since we have always been loading this code anyways.
I changed the execution check from `__REACT_DEVTOOLS_ATTACH__ ` to the
session storage.

## How did you test this change?

Everything works normal in my local build.