[ENH] Generate synthetic stallion data for testing.

[RihaanBH-1810]

This PR solves #1840 by replacing the get_stallion_data which downloads the dataset with a function which generates a similar dataset for testing.

Reference Issues/PRs

#1840

What does this implement/fix? Explain your changes.

Replace get_stallion_data usage in tests with get_stallion_dummy_data to avoid repeated network downloads and support offline CI.

What should a reviewer concentrate their feedback on?

Is this the right approach for generating synthetic data for tests ?

Did you add any tests for the change?

No

Any other comments?

PR checklist

• The PR title starts with either [ENH], [MNT], [DOC], or [BUG]. [BUG] - bugfix, [MNT] - CI, test framework, [ENH] - adding or improving code, [DOC] - writing or improving documentation or docstrings.
• Added/modified tests
• Used pre-commit hooks when committing to ensure that code is compliant with hooks. Install hooks with pre-commit install.
  To run hooks independent of commit, execute pre-commit run --all-files

[phoeenniixx]

Welcome to pytorch-forecasting @RihaanBH-1810!
Thanks for the PR, this is good!
Although, there are some genuine errors/failures, can you please have a look at them? Please let us know if you need any help!

[RihaanBH-1810]

Welcome to pytorch-forecasting @RihaanBH-1810! Thanks for the PR, this is good! Although, there are some genuine errors/failures, can you please have a look at them? Please let us know if you need any help!

Hello, sorry I got caught up with another project that I was part of, now that it's over I'll get this done asap.

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@dee16ad). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pytorch_forecasting/data/encoders.py	71.42%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1999   +/-   ##
=======================================
  Coverage        ?   86.53%           
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  Files           ?      165           
  Lines           ?     9764           
  Branches        ?        0           
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  Hits            ?     8449           
  Misses          ?     1315           
  Partials        ?        0           

Flag	Coverage Δ
cpu	86.53% <91.66%> (?)
pytest	86.53% <91.66%> (?)

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[RihaanBH-1810]

@phoeenniixx I have fixed all the errors/failures can you please take a look at it.