[Algorithm] TD3+BC

[BY571]

Description

Adds the offline RL algorithm TD3+BC as described in the paper A Minimalist Approach to Offline Reinforcement Learning.

Performance is verified for half-cheeta medium dataset:

Motivation and Context

Why is this change required? What problem does it solve? If it fixes an open issue, please link to the issue here. You can use the syntax close #15213 if this solves the issue #15213

• [ ] I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

What types of changes does your code introduce? Remove all that do not apply:

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds core functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [X] Documentation (update in the documentation)
• [X] Example (update in the folder of examples)

Checklist

Go over all the following points, and put an x in all the boxes that apply. If you are unsure about any of these, don't hesitate to ask. We are here to help!

• [X] I have read the CONTRIBUTION guide (required)
• [X] My change requires a change to the documentation.
• [X] I have updated the tests accordingly (required for a bug fix or a new feature).
• [X] I have updated the documentation accordingly.

[pytorch-bot[bot]]

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/rl/2249

• :page_facing_up: Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

:x: 4 New Failures, 1 Unrelated Failure

As of commit acc9baf52e8eced45cefd35c75fccc4ca6d76cf7 with merge base a151923d5e1eab68a8256fa02d0946a0f57bd5d0 ():

NEW FAILURES - The following jobs have failed:

* [Continuous Benchmark (PR) / CPU Pytest benchmark](https://hud.pytorch.org/pr/pytorch/rl/2249#27229976085) ([gh](https://github.com/pytorch/rl/actions/runs/9860746514/job/27229976085)) `Workflow failed! Resource not accessible by integration` * [Continuous Benchmark (PR) / GPU Pytest benchmark](https://hud.pytorch.org/pr/pytorch/rl/2249#27229976600) ([gh](https://github.com/pytorch/rl/actions/runs/9860746514/job/27229976600)) `Workflow failed! Resource not accessible by integration` * [Habitat Tests on Linux / tests (3.9, 12.1) / linux-job](https://hud.pytorch.org/pr/pytorch/rl/2249#27229978498) ([gh](https://github.com/pytorch/rl/actions/runs/9860746541/job/27229978498)) `RuntimeError: Command docker exec -t 37973d1520f3a39f9c4b301ce2be78d94e101d27e29255fb4e6e9463c168ed64 /exec failed with exit code 139` * [Unit-tests on Linux / tests-optdeps (3.10, 12.1) / linux-job](https://hud.pytorch.org/pr/pytorch/rl/2249#27229983480) ([gh](https://github.com/pytorch/rl/actions/runs/9860746535/job/27229983480)) `RuntimeError: Command docker exec -t 7cedf586ca5a98e3db66f8ca9d4dce6473d24227dac7d79bb9587ea3d04cd1fa /exec failed with exit code 1`

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

* [Unit-tests on Windows / unittests-cpu / windows-job](https://hud.pytorch.org/pr/pytorch/rl/2249#27229977152) ([gh](https://github.com/pytorch/rl/actions/runs/9860746531/job/27229977152)) ([trunk failure](https://hud.pytorch.org/pytorch/rl/commit/a151923d5e1eab68a8256fa02d0946a0f57bd5d0#27170792519)) `test/test_transforms.py::TestActionDiscretizer::test_trans_parallel_env_check[False]`

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[BY571]

Docstrings are updated :)