When using `pack build`, by default Pack will create two Docker
volumes for caching - one for the build layer cache, and the other
for the launch layer cache. Pack bases the names for these volumes
on the app image name, so that the next time a build is performed
with the same app image name, the associated cache is used for
that rebuild.

When libcnb-test runs tests, it intentionally uses a random Docker
image name for each new test, and then tears down the image and
any associated containers after the tests.

However, until now the Docker volumes automatically created by
Pack were not being removed, which can cause issues when
running the tests locally, since the Docker VM can run out of disk
space - as seen in #570. The leftover volumes can also be seen
in the tests log output added in #740.

Pack doesn't currently offer a "clean up the volumes associated
with this app name" feature, so we have to remove these volumes
manually. To do so we need the volume name - which we achieve
by generating a name ourselves, and passing it to `pack build`
using the `--cache` options, so Pack uses our volume name instead
of generating its own automatic volume name.

Since we're now cleaning up not only images but volumes too, I've
refactored the way resources are cleaned up, to reduce the amount
of duplication (since otherwise we'd need to handle the "still clean up
for expected failures" case for volumes too).

This new implementation also solves #735 and #736.

Fixes #570.
Fixes #735.
Fixes #736.
GUS-W-13195631.
GUS-W-14503186.
GUS-W-14503192.