Config restructure: distribute module configs via MQTT

[hikinggrass]

Changes to reduce configuration parsing effort by parsing it once by the manager and then distribute it to the modules via MQTT.

This is achieved by first parsing the MQTT settings from the config, passing these to the modules whilst spawning them. The modules themselves then ask for their module config via MQTT, which is in turn provided to them from the manager.

schemas, manifests, types, interfaces, error definitions are published as retained topics that modules can access when needed.

[a-w50]

We shouldn't need this, as the required cmake version is already > 3.13.
Furthermore, set(CMAKE_POLICY_DEFAULT_CMP0079 NEW) already enforces cmake_policy(SET CMP0079 NEW), so only the latter would be necessary. I also don't get the point of if(POLICY CMP0079)

[hikinggrass]

I'm also very confused why this is needed, since it should be the default. However on CMake 3.31 I get a

Attempt to add link library "gcov" to target "manager" which is not built
  in this directory.

  This is allowed only when policy CMP0079 is set to NEW.
Call Stack (most recent call first):
  tests/CMakeLists.txt:69 (append_coverage_compiler_flags_to_target)

error as if that policy isn't set.
the if(POLICY CMP0079) just ensures that the policy is available before setting it, maybe not necessary on CMake >= 3.13

[a-w50]

moving a const is indeed pointless. But it might be a better choice to make the constructor argument Config config_ instead of const ref and dropping the move.