Generate requirements files from pyproject.toml

[mdpiper]

This PR adds a nox session, "sync-requirements", to generate requirements files from the project requirements and optional dependencies listed in the pyproject.toml file.

Running the "sync-requirements" session results in:

|-- requirements.txt
|-- requirements-extra/
    |-- requirements-build.txt
    |-- requirements-dev.txt
    |-- requirements-docs.txt
    |-- requirements-notebooks.txt
    `-- requirements-testing.txt

Note all the optional/extra dependencies are listed in a separate requirements-extra/ directory.

I also updated the conda environment file environment-dev.yml to use these requirement files, installing the dependencies through pip.

[mdpiper]

I'll update the conda env file in the docs/ directory in a subsequent PR.

[coveralls]

Pull Request Test Coverage Report for Build 10255071348

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.949%

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Totals
Change from base Build 10084339047:	0.0%
Covered Lines:	1945
Relevant Lines:	1946

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💛 - Coveralls