docs: convert select/sidenav/slidetog/slider/snackb/sort to signals

[msmallest]

Description

Converts the following components to use signals

Part of an effort to address this issue about compatibility with new defaults: #33443

• Select
• Sidenav
• Slide Toggle
• Slider
• Snackbar
• Sort Header

I also switched one loop from tracking by identity to an index. This was because the diffing algorithm was throwing template warnings about how the array had multiple non-unique instances between only two possible items that kept being pushed in.

PR Scope

Another 6 component types updated.

Extras

1. Reference checklist gist: https://gist.github.com/msmallest/f77adb004b9e88c49b3a248bab90a26a?permalink_comment_id=6237249#gistcomment-6237249
2. The next PR will be a smaller chunk since I didn't want to overload this PR. And the Table examples (not including the one with an open PR, thanks for that) IMO warrant its own PR that I will finish things off with. Well, there is still stuff like experimental and CDK, but I mean finishing off the typical components.
3. edit: speaking of the point above, where would I find the pages to review the experimental examples? Do they have a docs page? I see use in the dev app, but I am not sure about the docs. I have since learned how the main pages of components reference particular examples by name, and there is the process of items in the index tending to by default be rendered in an Example page through a mechanism I am not familiarized with in the infra, but I am not sure where I would find any documentation embedded experimental examples.

[crisbeto]

This PR was merged into the repository. The changes were merged into the following branches:

• main: f4a0915
• 22.0.x: e4aaa64