text: Title: [Proposal] Allow to specify dtype for Discrete 
  Body: ### Proposal
  
  Add dtype argument to spaces.Discrete (similar to MultiDiscrete and Box).
  
  ### Motivation
  
  Currently the dtype is fixed to numpy.int64. However, often Discrete spaces are much smaller, resulting in a waste of memory.
  
  ### Pitch
  
  _No response_
  
  ### Alternatives
  
  _No response_
  
  ### Additional context
  
  _No response_
  
  ### Checklist
  
  - [X] I have checked that there is no similar [issue](https://github.com/Farama-Foundation/Gymnasium/issues) in the repo
  