New Metric: Soft Dynamic Time Warping (Soft-DTW)

[VijayVignesh1]

What does this PR do?

Fixes #3084

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

Added a new domain called timeseries to include Soft DTW loss.
Ref paper: https://arxiv.org/abs/1703.01541

Anyone in the community is free to review the PR once the tests have passed.
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📚 Documentation preview 📚: https://torchmetrics--3287.org.readthedocs.build/en/3287/

[VijayVignesh1]

@Borda Just wanted to get your initial opinion on this before I move forward. The softDTW uses dynamic programming which makes it really slow to work with on cpus. It's runs faster on gpus. Do you think it's worth continuing the effort?

[Borda]

@Borda Just wanted to get your initial opinion on this before I move forward. The softDTW uses dynamic programming which makes it really slow to work with on cpus. It's runs faster on gpus. Do you think it's worth continuing the effort?

I think it is very fine to have only the GPU version and raise an exception or a warning on the CPU