[ENH] Implement model loading functionality for InceptionTimeRegressor

[khansalman12]

Reference Issues/PRs

Addresses #2673

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What does this implement/fix? Explain your changes.

• Implementation: Adds load_model functionality for InceptionTimeRegressor and LITETimeRegressor to enable loading pre-trained regression ensemble models.
• Testing: Introduces a comprehensive test suite to validate the load_model functionality, including prediction consistency and error handling.
• Fix: Corrects the is_fitted flag for loaded models to ensure proper state tracking.

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PR Checklist

For all contributions

• I've added myself to the list of contributors.
• The PR title starts with [ENH] (enhancement).

For new estimators and functions

• Added load_model docstrings to the API documentation.
• (Optional) Added myself as a maintainer to relevant files.

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Does your contribution introduce a new dependency?

No new dependencies are introduced.

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