[V2]: Remove task type

[djdameln]

📝 Description

• This PR removes the task_type parameter from the library. In V2, we no longer explicitly need to set the task type. Instead, the task type is determined by the availability of the ground truth data and the choice of evaluation metrics.
• The engine and model are now agnostic wrt the task type. The model just generates whatever type of predictions it was designed to generate, and adds them to the output batch. During evaluation, the predictions may or may not be used, depending on the choice of metrics.
• The AnomalibDataset class still requires a notion of task_type to determine if it should include an empty mask in the dataset item for normal samples. Instead of passing an explicit task_type parameter to the class instance, we now infer the task type from the availability of ground truth masks on the file system, and store the inferred task type as metadata in the samples dataframe. A new task property was added to both AnomalibDatamodule and AnomalibDataset to easily retrieve the inferred task type when needed.

✨ Changes

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• 🔨 Refactor (non-breaking change which refactors the code base)
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• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔒 Security update

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Codecov Report

Attention: Patch coverage is 78.26087% with 10 lines in your changes missing coverage. Please review.

Please upload report for BASE (feature/v2@2f3d616). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/anomalib/data/datamodules/base/image.py	27.27%	8 Missing ⚠️
src/anomalib/data/datasets/base/image.py	85.71%	1 Missing ⚠️
...rc/anomalib/models/components/base/export_mixin.py	0.00%	1 Missing ⚠️

Additional details and impacted files

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##             feature/v2    #2450   +/-   ##
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  Files                 ?      307           
  Lines                 ?    13076           
  Branches              ?        0           
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  Hits                  ?    10221           
  Misses                ?     2855           
  Partials              ?        0           

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[samet-akcay]

massive trimming, thanks!