[envoy] Separate v8 in its own package

In order to speed up envoy&proxy builds, we decided to split up the v8 package in its own package. This package should generate a RPM containing the wee8.a file that's necessary at compile time by Envoy.

There must be two packages: One in community, so that we can install this RPM in the builder image; Another one in dist-git so that we can depend on it in product builds.

For more context about this decision, see OSSM-1227. For previous PoC work on this, see MAISTRA-1540.