feature: add resample() transformation function

[jakobchwastek]

Description

The resample transformation function offers multiple ways to adjust the sampling rate of gaze data. This function enables the adjustment of temporal frequency through both upsampling and downsampling. Additionally, it enables achieving a constant sampling rate for gaze data with inconsistent timestamps.

Resampling can be applied to both GazeDataFrame and entire Dataset. By default, it interpolates all columns of the resampled data frame. When applied to a GazeDataFrame containing multiple trials, the function resamples the data frame grouped by trial_columns. We exclude trial_columns from the interpolation in transforms.resample, as interpolation is not applicable to these columns. After processing, we fill the trial_columns.

The new sampling rate determined by the resampling process is stored in the Experiment object of the GazeDataFrame.

The resampling function processes timestamps with microsecond precision, supporting only sampling rates that divide 1,000,000.

Supported strategies for filling column values in newly created rows through resampling include forward filling, backward filling, linear interpolation, and nearest value interpolation.

Fixes issue #689.

Implemented changes

• [x] Implement transforms.resample function
• [x] Add transforms._apply_on_columns helper function, applying a function on nested and normal columns of a pl.DataFrame
• [x] Add logic handling resampling call in GazeDataFrame.apply
• [x] Add GazeDataFrame.resample with examples in docs
• [x] Add Dataset.resample

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• [x] Add resampling step in functional tests of processing gaze files and datasets.
• [x] Add unit tests in tests/unit/gaze/transforms/resample_test.py, testing for expected return values and exceptions
• [x] Test resampling of GazeDataFrame with test_gaze_dataframe_resample_expected in unit.gaze.gaze_transform_test
• [x] Test if assigning new sampling rate to Experiment in GazeDataFrame after resampling in test_gaze_dataframe_resample_changes_experiemnt_sampling_rate of unit.gaze.gaze_transform_test