updated changelog and fixed tests

com.unity.perception/CHANGELOG.md

 
 Unique seeds per Sampler have been replaced with one global random seed configured via the ScenarioConstants of a Scenario
 
-Replaced ScenarioBase.GenerateRandomSeed() with ScenarioBase.NextRandomSeed()
+Replaced ScenarioBase.GenerateRandomSeed() with ScenarioBase.NextRandomState()
 
 ### Deprecated