Add zip-apex

This adds support for an apex-like file where the payload is a zip
file instead of a FS image. This makes it easier to examine and use
without root. These can also be built for the host.

This can be controlled using the 'type' modifier in the apex build
rule. 'type' may be "image" to build an apex file called {name}.apex
with an FS image payload, "zip" to build an apex with called
{name}.zipapex with a zip-file payload or "both" to build both. By
default we will use "image".

This also adds support for setting apex rules to
"host_supported: true".

Test: cd art/build/apex; mma; examine the com.android.runtime.host.zipapex
      artifact.
Test: go test android/soong/apex -v
Bug: 120436895

Change-Id: I534d330672211ac5ccc3bd5a0c89b9fc507bf51e