Return 3.x um reflectance with the same dtype as the NIR data

[pnuu]

This PR keeps the dtype of the input NIR data for the calculated reflected portion of it. For non-Numpy/Dask inputs float64 is used.

The approach is pretty simplistic, I didn't want to start passing dtype to the parent class of the Calculator (RadTbConverter)

• Closes Near infrared reflectance calculation does not preserve input dtype #205
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented
• Add your name to AUTHORS.md if not there already

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (6f3b523) 89.96% compared to head (234ac91) 89.92%.

Files	Patch %	Lines
pyspectral/tests/unittest_helpers.py	50.00%	5 Missing ⚠️
pyspectral/radiance_tb_conversion.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #206      +/-   ##
==========================================
- Coverage   89.96%   89.92%   -0.04%     
==========================================
  Files          23       23              
  Lines        2580     2571       -9     
==========================================
- Hits         2321     2312       -9     
  Misses        259      259              

Flag	Coverage Δ
unittests	89.92% <94.23%> (-0.04%)	⬇️

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[mraspaud]

I don't think we need to pass the dtype to the class constructor, we can just use the temp dtype directly in tb2radiance right?
I think it would look better, and that way we avoid upscaling and downscaling again, if we ensure that the planck function doesn't do the upscaling to start with.

[pnuu]

As @mraspaud suggested, I now handle the type conversion/preservation in blackbody and rad2bt methods. Along the way I needed to convert some tests to pytest so I could parametrize the dtype stuff.

[mraspaud]

Looks good, I just have a few comments inline.

[mraspaud]

Looks great, thanks for all the effort @pnuu !

[mraspaud]

@adybbroe do you want to have a last look before we merge thist?

[adybbroe]

LGTM. Nothing to add, nice work.