Descriptions in trigger schema & small cleanup

[ArturSztuc]

This PR goes together with:

1. Removing HSIpassthrough & reorganisation of bitword variable setup trigger#361
2. Removing obsolete trigger configs & new default for TCDataProcessor::td_readout_limit daqsystemtest#154

Changes:

1. Added descriptions to the trigger schemas
2. Removed few that are obsolete/not used attributes/objects
   • This includes HSI passthrough. It was already removed in v4, and somehow it was not removed in v5. This included removal of the hsi-passthrough code in the trigger repository (see the trigger PR above)
3. Changed the default value for TCDataProcessor::td_readout_limit from 100 to 1,000,000: it used to be in terms of milliseconds, now it is in terms of ticks.

Tested by running integration tests (all pass), and the example test configuration.

[glehmannmiotto]

LGTM