Support composite observation space with proper min max in manager based env

[ooctipus]

Description

This PR supports enables ManagerBasedRLEnv to properly support gymnaisum's composite observation gym.spaces.Dict at term-level with proper min, max specification. The benefit is that this will give rl-library a clearer signs how to pre-process the obseravtion data.

Before:
All terms are assigned with gym.Spaces.Box(min=-np.inf, max=np.inf), one problem with this is that from rl-library side, is that some rl-libraries network construction depends heavily on observations space details. RL-library (e.g. sb3) looks at gym.Spaces.Box.min and gym.Spaces.Box.max to determine if they need to normalize it at library side.

After:
this PR utilizes on obs_terms's clip to determine if gym.Spaces.Box should be stricter. For example, environment obs_term returning gym.Spaces.Box(min=0, max=255) will be automatically detected by sb3, and a proper scalling be applied automatically. whereas gym.Spaces.Box(min=-inf, max=inf) will fail.

while no special case is treated for gym.Spaces.Box(min=-1, max=1), but this will makes the rl-library easy to figure out that this term is already clipped, not more transformation needed.

Type of change

• New feature (non-breaking change which adds functionality)

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there