[TASK] Add submodules to "Styleguide" backend module

Over time, EXT:stylguide has expanded its range of functions.
To clarify the separation between styles and components, as well
as the functionality of creating example page trees, the contents
of the backend module "Styleguide" are divided into submodules.

Resolves: #104358
Releases: main
Change-Id: I9548567265633b66da3fadd4f0f5b07f39f79ae8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85186


Reviewed-by: Benjamin Kott <benjamin.kott@outlook.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Benjamin Kott <benjamin.kott@outlook.com>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>