Add wrappers for TorchRL training workflow

[fyu-bdai]

Description

Adds TorchRL module wrappers, PPO runner, and PPO runner cfg for training IsaacLab environments with TorchRL.

This PR is the first in a series of three that together, adds a complete training pipeline for the Anymal-D training environment using torchrl. This PR contains core wrapper modules that should be merged first.

Related PRs:
#1179 Adds torchrl play and train scripts.
#1180 Adds Anymal-D torchrl training configuration.

Fixes #1181

⚠️ Not Supported

• Empirical normalization.
• Recurrent networks.
• Training with Neptune logger.

🤔 Issues

• Training with num_envs == 1 doesn't work.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

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

[fyu-bdai]

Can Vincent Moens also get tagged as a reviewer?

[Toni-SM]

In my opinion, non-wrapper code (e.g.: torchrl runner code) should be in the source/standalone/workflows folder.

source/standalone/workflows
├── torchrl
│   ├── ppo/      <-- code here
│   ├── cli_args.py
│   ├── play.py
│   └── train.py

Having the PPO runner code in extension will generate non-Isaac Lab related version changes and changelog records when the code need to be modified.

[fyu-bdai]

In my opinion, non-wrapper code (e.g.: torchrl runner code) should be in the source/standalone/workflows folder.

source/standalone/workflows
├── torchrl
│   ├── ppo/      <-- code here
│   ├── cli_args.py
│   ├── play.py
│   └── train.py

Having the PPO runner code in extension will generate non-Isaac Lab related version changes and changelog records when the code need to be modified.

I realized this causes issues with the environment specific PPO configurations, which needs to import the TorchRL PPO runner cfgs. I can move only the configs to omni.isaac.lab_tasks.utils.wrappers, but that would split the location of the torchrl runner and torchrl runner cfg. I have elected to move them back as they are for now.