Also build gtest and g1 runtimes

Following #239 which allows all of network, client and runtime release for gdev: we also need the same for gtest and g1.

The network part should already be OK (not tested though), but the runtime part is not: the runtime release process only builds gdev runtime, it should also build gtest and g1 simultaneously and publish the 3 srtool outputs in the release as well as attaching the 3 runtimes.

The xtask runtime-release command only work with 1 runtime at a time (based on SRTOOL_OUTPUT env variable). It will require to handle three at a time.