Add pipeline value operations tests

[edoyango]

The tests covers all the operation classes in operations/{dask,numpy,xarray}/values.py. Some important changes:

• refactored xarray fillna to behave like numpy fillna
  • before, xarray fillna only filled nans, whereas numpy fillna also filled in positive and negative infinities.
• completed the implementation of dask fillna
  • This was raising a NotImplementedError, and just needed to add a missing arg in da.nan_to_num to make it work.
• use the Replace class instead of replace_value class from pyearthtool.data.transforms.mask as replace_value doesn't exist anymore.
• Renamed ForceNormalised operation to Clip since that matches the functions in dask/numpy/xarray
  • also refactored the classes to use the corresponding clip function
  • This is probably the most opinionated change here, happy to change back if it's a problem.
• fixed a problem in xarray.Derive where Derive.apply_func was also updating the input dataset.
• fixed a warning in pyearthtools.data.transforms.derive by replacing the deprecated Dataset.drop with Dataset.drop_vars

[coveralls]

Pull Request Test Coverage Report for Build 20835553598

Details

• 151 of 152 (99.34%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.9%) to 65.91%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/data/src/pyearthtools/data/transforms/derive.py	7	8	87.5%

Totals
Change from base Build 20305027296:	0.9%
Covered Lines:	10711
Relevant Lines:	15893

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💛 - Coveralls