ATR-19262: Support FTK b-jet chains with the ALLTE implementation

Justification: A misconfiguration of FTK b-jet chains affecting multi b-jet chains, which are configured with the so-called ALLTE implementation for b-jet chains. For them, FTK algorithms are not scheduled. Conversely, single b-jet chains are correctly implemented, since they fo not use the ALLTE implementation. The solution is to modify the ALLTE configuration in order to schedule FTK algorithms.

This MR also adds GSC for FTK multi b-jet chains, and goes together with !20263 (merged)

Tests:

trigtest.pl --test BjetSliceAthenaTrigRDO --run BjetSliceAthenaTrigRDO --conf TriggerTest.conf produced no difference w.r.t. the nominal release.

Jira: ATR-19262

Notes: bug

Tagging @baines, @aranzazu, @jmontejo, @lidiaz and @sekula