MOC TS map rebases on v0.3.x

[Yong2Sheng]

This PR adds the method to do multi-resolution (also called multi-order coverage, MOC) TS map fitting.

Changes to FastTSMap

1. FastTSMap is the parent class of MOCTSMap

2. I need to make several changes to FastTSMap to make it work with MOCTSMap:

   • Add pixel_idx parameter for fast_ts_fit.
     • This parameter is the index of the pixels fitted by FastTSMap.
     • This is added since we only fit a portion of the multi-resolution map. So I need to record the indices of the fitted pixels to match the likelihood values.
     • Note it's index of the pixels in a multi-resolution map, not the unique numbers of the pixels.
   • Add a new function zip_comp to generate the inputs for multiprocessing.
     • I used itertools.product before. However, it will cause duplicated fittings in MOCTSMap.
     • So I use zip_comp to replace it.

New module MOCTSMap.

1. This is the new module responsible for multi-resolution TS map fitting.
2. It checks the likelihood during each iteration, and only fit the child pixels of the mother pixels that meets the criterion.
3. Add unit test for moc_ts_fit.py.
4. Fixed a bug in Add multi-resolution TS map fitting  #248 where the MOC TS map values are integers. Not sure how this could affect/improve the current result, I will do some tests.

Changes to the TS map tutorial

1. I renamed the tutorial notebook back to the original one name Parallel_TS_map_computation.ipynbso we can keep everything self-consistent
2. I added Example 4, which fits the Crab with the multi-resolution map.

Please let me know if you have any questions and suggestions. Thank you!

[codecov]

Codecov Report

Attention: Patch coverage is 92.68293% with 9 lines in your changes missing coverage. Please review.

Project coverage is 79.80%. Comparing base (96057d5) to head (c4172c6).
Report is 8 commits behind head on v0.3.x.

Files with missing lines	Patch %	Lines
cosipy/ts_map/moc_ts_fit.py	95.14%	5 Missing ⚠️
cosipy/ts_map/fast_ts_fit.py	76.47%	4 Missing ⚠️

Files with missing lines	Coverage Δ
cosipy/__init__.py	100.00% <100.00%> (ø)
cosipy/ts_map/__init__.py	100.00% <100.00%> (ø)
cosipy/ts_map/fast_ts_fit.py	57.36% <76.47%> (+3.13%)	⬆️
cosipy/ts_map/moc_ts_fit.py	95.14% <95.14%> (ø)

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[israelmcmc]

Thanks @Yong2Sheng. Looks good to me, I'm merging!

• I'll wait to merge Adopt histpy 2 features in cosipy #343 and No magic cells in automatic run_tutorial.py and other related changes #349 before merging this to develop, but I merged both of them to this PR locally (in this branch). After resolving some small conflicts, I run the test and the ts map tutorial with no problem. The executed tutorial is attached:
  tutorials.zip

• I'm planning to make a new 0.3.5 release in 1-2 weeks, I'll include this.

[Yong2Sheng]

Thank you @israelmcmc for reviewing and merging this PR!