Generate the `NavigationItem`-s as part of adev/shared-docs pipeline and use the output JSON files instead of the hardcoded objects in the `sub-navigation-data.ts`.
PR Close#59355
To increase the ease of development we are moving @angular/docs into the adev directory within this repo. While
we are doing this to improve our development experience in the short term, efforts are also in place
to maintain a division between this @angular/docs (shared) code and adev itself, so that it can be extracted
back out in the future when components is ready to leverage it as well.
PR Close#57132