All-in-one build total refactor

[marvinmarnold]

Why The build process is confusing. This is one of two proposals on how to structure the Dockerfile in order to improve things.

How One anti-pattern in how things are done currently is that this Dockerfile is responsible for building other repositories, specifically nebraltd/packet_forwarder and nebraltd/lora_gateway. This PR copies those libraries directly into source control. Copying libraries using git clone within the Dockerfile should always be avoided IMHO.

The other proposal builds lora_gateway and packet_forwarder independently.

References

• Part 1 of other proposal: https://github.com/Lora-net/lora_gateway/pull/172
• Part 2 of other proposal: https://github.com/Lora-net/packet_forwarder/pull/145

[marvinmarnold]

The decision is to build all dependent projects (nebraltd/lora_gateway, nebraltd/packet_forwarder, and nebraltd/sx1302_hal) in their respective repos and reference built assets from hm-pktfwd. Will open a new PR that implements like that.