refactor(docs-infra): scope TOC styles to the `<aio-toc>` element (#40704)
refactor(docs-infra): scope TOC styles to the `<aio-toc>` element (#40704)

This commit ensures that all styles for the TOC (which are defined in
`_toc.scss`) only apply to elements inside an `<aio-toc>` element. This
will prevent the styles accidentally taking effect on a different part
of the app.

PR Close #40704

ocombe/angular,angular-indonesia/angular,alxhub/angular,shairez/angular,JiaLiPassion/angular,gnomeontherun/angular,brandonroberts/angular,angular-indonesia/angular,shairez/angular,ocombe/angular,alxhub/angular,alxhub/angular,angular-indonesia/angular,angular/angular,gnomeontherun/angular,gkalpak/angular,ocombe/angular,manekinekko/angular,brandonroberts/angular,gnomeontherun/angular,alxhub/angular,JiaLiPassion/angular,mgechev/angular,ocombe/angular,alxhub/angular,gkalpak/angular,ocombe/angular,mgechev/angular,brandonroberts/angular,JiaLiPassion/angular,manekinekko/angular,shairez/angular,gkalpak/angular,manekinekko/angular,ocombe/angular,JiaLiPassion/angular,angular/angular,angular/angular,brandonroberts/angular,mgechev/angular,manekinekko/angular,mgechev/angular,mgechev/angular,manekinekko/angular,brandonroberts/angular,gnomeontherun/angular,angular-indonesia/angular,gkalpak/angular,shairez/angular,shairez/angular,manekinekko/angular,brandonroberts/angular,angular/angular