Add Phase Resolved Analysis tools (#395)

[KoothodilAbhijithAugustine]

Fixes #395
Implements the tool to obtain a phasogram as described in issue #395.
Adds PulsarAnalyzer class, phase_resolved_analysis module, and tutorial notebook.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 147 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.85%. Comparing base (dc46b9b) to head (e9f313b).
⚠️ Report is 91 commits behind head on develop.

Files with missing lines	Patch %	Lines
cosipy/phase_resolved_analysis/pulse_profile.py	0.00%	145 Missing ⚠️
cosipy/phase_resolved_analysis/__init__.py	0.00%	2 Missing ⚠️

Files with missing lines	Coverage Δ
cosipy/phase_resolved_analysis/__init__.py	0.00% <0.00%> (ø)
cosipy/phase_resolved_analysis/pulse_profile.py	0.00% <0.00%> (ø)

... and 3 files with indirect coverage changes

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[israelmcmc]

Thanks @KoothodilAbhijithAugustine. While this is reviewed, can you please add unit tests that cover the new code?

There's an explanation here: https://cositools.github.io/cosipy/dev/unit_tests.html
And multiple example here: https://github.com/cositools/cosipy/tree/develop/tests