[Feature] Add TanhModuleConfig

[bsprenger]

Description

This PR adds the TanhModuleConfig dataclass, which corresponds with the already-existing TanhModule. This PR also adds a test for the new config dataclass.

Motivation and Context

Adding this config dataclass will allow for directly instantiating a TanhModule, simply by defining the relevant fields in the config yaml.

Issue: #3256

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

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[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/rl/3255

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