We now include the prelude in so many places, this simplifies how we can
present how `cargo-test-support` works.
Yes, this included some `use` clean ups but its already painful enough
walking through every test file, I didn't want to do it twice.
While this is noisy and hides other deprecations, I figured deprecations would
make it easier for people to discover what tasks remain and allow us to
divide and conquer this work rather than doing a heroic PR.
In theory, this will be short lived and we'll go back to seeing
deprecations in our tests.
This introduces a new `CacheLocker` which manages locks on the package
cache. Instead of either being "locked" or "not locked", the new locker
supports multiple modes:
- Shared lock: Cargo can read from the package sources, along with any
other cargos reading at the same time.
- Download exclusive lock: Only one cargo can perform downloads.
Download locks do not interfere with Shared locks, since it is
expected that downloading does not modify existing files (only adds
new ones).
- Mutate exclusive lock: Only one cargo can have this lock, and it also
prevents shared locks. This is so that the cargo can modify the
package cache (such as deleting files) without breaking concurrent
processes.
