R2D2 optimize and benchmark

[kan-s0]

Is your feature request related to a problem? Please describe.
Currently, the state type stored as a transition in R2D2 is too large as float64. And if the sequence length is lengthened accordingly, the existing buffer size is too large.

Describe the solution you'd like

• Change the state type of transition to unit8.
• Reduce the buffer size of the config.
• R2D2 atari benchmark

Describe alternatives you've considered

• Fixed size when adding state to _transition in agent interact callback.

Additional context

• R2D2 atari benchmark