DPL: add unit test for gui::showTopologyNodeGraph

DPL: adapt to support new FairMQ versions

FairMQ changed `FairMQDevice::fDevice` to a shared_ptr from a
unique_ptr. This makes sure we can compile DPL with both version and
introduces an helper to handle this kind of situations in the future
when updating might not be an option.

Use LOG(INFO) instead of Info()

This is a bug fix. I found that the Info() API (from ROOT?) interferes
with the LOG(INFO) system from FairLogger. Since the latter is also used for
control in DPL, some control messages were sometimes not dispatched
correctly leading to non-exiting DPL workflows.

DPL: create index of distinct InputRoutes

While being just a minor performance improvement, this refactoring
will come useful with the coming integration of proper Lifetime for
objects.

DPL: improve ROOT test

DPL: improve ROOT test

DPL: add missing forward declaration

Use DPL completion policy in TPCDigitWriter

This commit uses the DPL completion-policy mechanism
to write TPC digits or labels into the ROOT file as soon
as they are available in the writer device.

The writer device now takes a lot less memory and distributes its
CPU activity more evenly.

This concludes Jira ticket [O2-268].

DPL: add initial InfoLogger integration to DPL

* InfoLogger can now be used as a Framework service by
  providing the --infologger-backend commandline option.

Further integration with FairLogger coming in a different PR.

Ignore PCG in clang-format