Put the workspace crates first in the side panel

[Boiethios]

Describe the problem you are trying to solve

I try to document a project with a few crates in a workspace. The issue is that there is a ton of dependencies (that I'd like to browse when needed), and my crates are drowned in the middle of those dependencies in the side panel.

It's impossible to see in a glance which crates are in the project, and thus to browse the project correctly.

Describe the solution you'd like

I think that the crates from the workspace should come first if the side panel, and then the dependencies. If there are 2 crates foo and bar in the workspace, the panel should looks like that:

CRATES
---------
bar
foo
---------
all
the
dependencies

[ehuss]

Transferred to rust-lang/rust, as that is where rustdoc lives.

Also, this is somewhat similar to #16328 and #81031.

[Boiethios]

Sorry for that: since I type cargo doc to generate the doc, I thought it was a cargo issue.