In some cases in our tests we can define multiple overrides for a given class. As a result, only the last override is actually applied due to the fact that we store overrides in a Type<->Override map. This update changes the logic to keep all overrides defined in a given test for a Type (i.e. Type<->Override[] map) and applies them one by one at resolution phase. This behavior is more inline with the previous TestBed.
PR Close#27734
