Fix default initialization of CAT values in Matter Testing Support (#22116)
Fix default initialization of CAT values in Matter Testing Support (#22116)

This fixes the default initialization of the `controller_cat_tags` field
in `MatterTestingSupport` class to correctly be initialized to an empty
list, since that is what is expected by FabricAdmin.NewController (and
others).

Testing:

Repro'ed the failure described in #22114, and then confirmed this fixes
it.
project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip