Rollup merge of #124772 - madsmtm:apple-platform-support-docs, r=oli-obk

Refactor documentation for Apple targets

Refactor the documentation for Apple targets in `rustc`'s platform support page to make it clear what the supported OS version is and which environment variables are being read (`*_DEPLOYMENT_TARGET` and `SDKROOT`). This fixes rust-lang/rust#124215.

Note that I've expanded the `aarch64-apple-ios-sim` maintainers `@badboy` and `@deg4uss3r` to include being maintainer of all `*-apple-ios-*` targets. If you do not wish to be so, please state that, then I'll explicitly note that in the docs.

Additionally, I've added myself as co-maintainer of most of these targets.

r? `@thomcc`

I think the documentation you've previously written on tvOS is great, have mostly modified it to have a more consistent formatting with the rest of the Apple target.

I recognize that there's quite a few changes here, feel free to ask about any of them!

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CC `@simlay` `@Nilstrieb`

`@rustbot` label O-apple

Author: matthiaskrgr