[config,pipeline] Make number of TBB tokens per stream a configurable setting

Description:

Currently, TBB concurrency is constrained to a number of live tokens defined as 4 * number of threads for each stream.

Per discussion here, this value, or an equivalent control over TBB resources, should be user-defined through a configuration file option.

Fix:

MR !75 (merged) introduced a variable fMaxTokensPerThread to DAQ Pipelines (defaulted to 4), which needs to be connected to the configuration abstraction after the planned migration to JSON5.

Following that, grid optimization should be performed to better understand the impact of live tokens on multi-pipeline performance.