Implement Beta-Dreamer in DreamerV3 architecture

[aarunsrinivas5]

Replace vanilla actor critic with epistemic risk seeking actor critic (ERSAC) variant using risk seeking exponential as opposed variance reward bonus in the DreamerV3 architecture to determine the benefits of risk modulation using exponential function. ERSAC paper: https://arxiv.org/pdf/2302.09339; Exponential TD Learning paper: https://johnbaras.com/wp-content/uploads/2023/08/22-29-Exponential_TD_Learning_A_Risk-Sensitive_Actor-Critic_Reinforcement_Learning_Algorithm.pdf