Move all full-node logic under a build tag

[v1rtl]

Summary

It makes no sense to run a full node in a browser, inside a EFI module, Android or on a cheap microcontroller. In order to simplify the logic, decrease bundle size and improve perf, build tags could be utilized.

Motivation

Simplification of the architecture of Bee for low-end targets. Significant decrease of bundle size.

Implementation

A build tag that is enabled by default which can be turned off, which would exclude all full node logic from the compilation. A name could be -tag full-node

Drawbacks

Need to be careful not to affect other parts of the logic that might depend on full node checks