## Summary
This is a small correctness improvement that ensures that we avoid using
stale cache entries for local dependencies in the install plan. We
already have some logic like this in the source distribution builder,
but it didn't apply in the install plan, and so we'd end up using stale
wheels.
Specifically, now, if you create a new local wheel, and run `pip sync`,
we'll mark the cache entries as stale and make sure we unzip it and
install it. (If the wheel is _already_ installed, we won't reinstall it
though, which will be a separate change. This is just about reading from
the cache, not the environment.)
## Summary
This PR enables `puffin clean` to accept package names as command line
arguments, and selectively purge entries from the cache tied to the
given package.
Relate to #572.
## Test Plan
Modified all the caching tests to run an additional step to (1) purge
the cache, and (2) re-install the package.
This PR adds caching support for built wheels in the installer.
Specifically, the `RegistryWheelIndex` now indexes both downloaded and
built wheels (from registries), and we have a new `BuiltWheelIndex` that
takes a subdirectory and returns the "best-matching" compatible wheel.
Closes#570.
Charlie Marsh