Add sudo mode for admins

[LawnGnome]

This PR adds a concept of "sudo mode" for admins logged into crates.io. Actions that require admin privileges will be disabled by default unless the admin explicitly turns on admin actions from the user menu, at which point they will be given privileges for six hours or until they disable admin actions again from the user menu. Sudo mode is per-user, per-browser; it is not synced across multiple browser sessions, even for the same user.

These cases look like this:

In addition to this, a new PrivilegedAction component has been added that can gracefully handle rendering controls that can be used either by a regular user or an admin in sudo mode, including showing the control in a disabled mode when an admin is logged in but they have not enabled sudo mode. The disabled mode looks like this:

(I don't know why the tooltip wraps, but I don't really care much, honestly.)

Finally, the existing yank/unyank functionality has been wrapped in PrivilegedAction, both because it needs to be anyway, and because it demonstrates how this is used in practice.

This is likely best reviewed commit by commit. (In theory, each of these could be a PR unto themselves, but I don't see much point splitting this out without the motivating example of how it interacts with the yank button.)

Open questions:

• Is six hours the appropriate amount of time for sudo mode to be enabled by default? (In theory, we could actually allow the admin to specify how long they want, but that seems unnecessarily complex.)
• Is it OK that sudo mode is per-browser?
• Do we want a visible indicator next to the user avatar that sudo mode is enabled? I've used a 🧙 emoji as a placeholder, but if we want this, we probably want an actual icon of some kind.
• Should this just be called "sudo mode" in the UI as well?
• How many lints have I accidentally broken because I can't figure out how to configure my local environment in the same way as CI expects? 😬

This implements step 1 of the plan laid out in #8049.

[LawnGnome]

I've pushed new commits in response to the review. (Thanks!)

To simplify re-review, I haven't rebased them into the previous set of commits, but (if approved) I'll reorder and squash them down as appropriate before merging.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.56%. Comparing base (3044bbf) to head (78c0f77).
Report is 15 commits behind head on main.

❗ Current head 78c0f77 differs from pull request most recent head a5c3387. Consider uploading reports for the commit a5c3387 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8210   +/-   ##
=======================================
  Coverage   87.56%   87.56%           
=======================================
  Files         271      271           
  Lines       26983    26983           
=======================================
  Hits        23628    23628           
  Misses       3355     3355           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Turbo87]

One thing we should add for this change is an acceptance/application test that asserts that the full flow with the sudo mode is working correctly. This can be added in a follow-up PR though and this seems useful enough that I'll merge it without the test already :)