add TCT test to check file merging
Add a test for merging of AOD, DAOD_IDTIDE, DESD_MCP pool files with the same configuration as currently used at Tier0. It will read unmerged inputs from cvmfs (a recent run reconstructed with release 23.0.31) rather than running a dedicated reconstruction step. Output comparisons are enabled (against the previous nightly), only for a small number of events (5) as the main purpose would rather be to catch missing branches or metadata differences.