Add Archive of Rust Stable Standalone Installers

[yerke]

Closes #676

This PR adds a new page "Archive of Rust Stable Standalone Installers" that contains a list of tables of previous stable Rust version standalone installers.

Currently it works for all versions > 1.8. Versions <= 1.7 do not have v2 toml manifests. See Zulip for details.

@shepmaster @ojeda Is this what you had in mind?

Screenshots:

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[yerke]

r? @shepmaster

[yerke]

r? @ehuss

[yerke]

@ehuss thanks a lot for taking a look. I addressed your feedback.

[ojeda]

@shepmaster @ojeda Is this what you had in mind?

Yeah, thanks a lot!

It could be nice to have a matrix instead (but that makes it complex, i.e. empty cases would need to be handled, plus it may be not great scrolling horizontally, so it could require breaking the table in several anyway), or a selector, or at least a way to jump quickly to the right version.

But I would not worry about any of that -- even if it is just a dump of links, it is useful :)

[ehuss]

I am not on the infra or release teams, so I'm not sure I am the appropriate person to be approving things on their behalf. Perhaps @Mark-Simulacrum would give the green light. I'm fine with the implementation barring #733 (comment) getting resolved.

[Mark-Simulacrum]

This looks fine to me with one implementation and one wording note.

[yerke]

@Mark-Simulacrum Do you mind taking another look when you get a chance? Thanks.

[Kobzol]

Could you remove the merge commits please?

[yerke]

@Kobzol done!

[Kobzol]

The previous comments have been resolved, so I think that we can merge this.