cuttlefish: Stop building the CVD host package tarball by default.

This change causes us to stop building the CVD host package during
the default `m` build, as this is one of the most time consuming steps
of incremental builds, taking around a minute on my machine. Instead,
we build a directory containing the host package contents. A companion
change to acloud teaches it to upload the directory if it exists.

The host package tarball will continue to be built with `m dist` and `m
hosttar`. When building the host package, just create it from the package
contents directory instead of going through a zip file as we were before.

Bug: 273862156
Change-Id: Id7ab47cd5a2e96d073fcc21ed82d3719119df6b9