This commit updates the table of contents functionality to clean up correctly whenever the user
navigates to other pages and nodes are removed from the DOM.
Currently, calling `renderComponent` with the `TableOfContents` keeps creating a new table of contents
component without removing the previous one, as they are created manually.
This leads to memory leaks because the components cannot be collected properly, even if the user
navigates to the home page where there is no TOC component.
PR Close#58034
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
