GeezerVison

…156682)

* Docs: split builtins to their own page from library

* review feedback

* addressed Hugo's feedback

* update the What's Next page

* one more wording tweak

* move builtins to their own directory. fix the reference name

* moved pages need to be noted in tools/removed-ids.txt

* add Python to the builtins reference title

* add sphinxext-rediraffe for the library->builtins split

* update check-html-ids to handle rediraffe redirects

* now we don't need (page missing) for the redirected pages

* update other references to moved pages

* A seealso from builtins to library

* make a nice section for rediraffe settings

* move the builtins note to the end, as a seealso

* address merwok's comments

* cache looking for ids in files

* simplify the intro paragraphs
(cherry picked from commit 59c4bdd)

Co-authored-by: Ned Batchelder <[email protected]>