Move launching pad to its own page

[ehuss]

This changes the governance page so that the launching pad has its own page. All the working groups are moved from the top-level page to show up under the launching-pad page instead.

One of the intentions here is to support showing team members for non-working-groups in the launching pad. Currently there is no way to view them.

I suspect that we will keep the launching pad for a long time, as it will take a while to reorganize everything. It's also unclear if we should keep the launching-pad indefinitely, or if there will be some point where we will remove it. I think once we reach that point, then we'll just remove the launching-pad page.

The old links for things like https://www.rust-lang.org/governance/wgs/wg-security-response continue to work, but there are no direct links to them anymore.

[ehuss]

This requires a companion change to rust-lang/team for this to work (rust-lang/team#1643).

cc @jamesmunns I don't know if you think this might be a good idea.

Unfortunately I don't have a good way to show you a preview of what this looks like. Just imagine https://www.rust-lang.org/governance without the green "Working Groups" section, and instead a link in the "Teams" section to the Launching Pad that has a list of all the launching-pad teams and their members.

I don't know if this is really the best approach, but I couldn't think of a good alternative. We could keep the "Working Groups" list at the bottom, but I don't know why we would do that. That is not a complete list, and I'm not sure why we would want to highlight them on the top-level page.

[apiraino]

Question without seeing the changes: how does the website will behave with links currently indexed by search engines? Will there be any broken links? Autoredirects?

[ehuss]

The old working-group pages continue to exist as they did before.