Add (A)syncVectorEnv support for sub-envs with different observation spaces

[pseudo-rnd-thoughts]

Description

In order to add Meta-World environments to use the Sync/Async Gymnasium methods, a change needed to be made in order to batch observations that have different low/high values.

This change allows the user to specify one of 3 modes for batching observations:

• 'same': current method of having the same observation space for all environments
• 'different': method that allows for different observation spaces to be batched together, given the observation spaces are the same size
• tuple[gym.Space, gym.Space] object: allows the user to input a specific method not covered by the 2 above modes to define themselves what the observation and single observation spaces are.

For 'same', sub-environment are tested to check they are all the equivalent
For 'different' and custom spaces, sub-environment are tested to check they share a common dtype and shape