Take a simpler test position for slats

DPL: improve ScopedExit (AliceO2Group#3798)

DPL: add error policy

By default one single error terminates the workflow when running in
batch mode. Use --error-policy=wait to wait.

By default one single error is reported but not fatal when running in
GUI mode. use --error-policy=quit to quit the whole workflow and
the GUI.

GPU: Fix GPU TRD Tracking

GPU: Fix creation of connected components for resolve kernel.

GPU: Fix vectorised memcpy in gather kernel.

Improvements to the DPL RootTreeWriter spec generator

- Adding support for auxiliary inputs, i.e. inputs which are not connected to
  a branch definition. Auxiliary inputs can be accessed in the preprocessor
  callback.
- Making the callback variants default constructible.
- Handling initialization of CustomClose callback

Update MCTrack.h

Increase ClassDef version ID (since members have been added)

Revert default shmem (AliceO2Group#3680)

Use of material map in the track propagator (AliceO2Group#3682)