refactor pyproject and workflows

[Ravencentric]

• Deduplicate pyproject.toml. Removed the [project] section because it was essentially useless since poetry doesn't support it and completely switched to [tool.poetry] as the canonical source of metadata
• Drop 3.7 and 3.8 (https://endoflife.date/python). Httpx only supports >=3.8 and pytest-httpx only supports >=3.9.
• Add Python 3.12 to the test matrix
• Drop flake8, ruff can do the same thing so I switched to that
• Use poetry in the workflows
• Remove upper constraint from non-dev dependencies as this was causing issues with any library that would try installing it without having the same upper constraint
• Closes httpx too old version #93

[coveralls]

Pull Request Test Coverage Report for Build 10860587733

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.07%) to 89.025%

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Totals
Change from base Build 10703468182:	-0.07%
Covered Lines:	850
Relevant Lines:	924

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💛 - Coveralls