ADAP-1115: Move to hatch and pyproject.toml

[mikealfare]

We are moving to a monorepo that uses pyproject.toml and hatch. This requires a series of migrations, including this one. This PR inclues:

• update from setup.py/dev-requirements.txt to pyproject.toml/hatch.toml
• move tool config (e.g. mypy and pytest) into pyproject.toml
• update workflows regarding these moves
• delete configs that no longer apply (e.g. tox.ini, pytest.ini, etc.)

[github-actions]

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[mikealfare]

Since CI is target branch based, here's the actual integration test run: https://github.com/dbt-labs/dbt-snowflake/actions/runs/11883218656

[mikealfare]

Integrations that run against the workflow in this branch:
https://github.com/dbt-labs/dbt-snowflake/actions/runs/12215746378

[mikealfare]

Integration tests running against the workflow in this branch, now using a hard pinned ubuntu image:

https://github.com/dbt-labs/dbt-snowflake/actions/runs/12241551824

Previous runs were passing on macos and windows, but not ubuntu. GH is currently migrating ubuntu-latest from 22.04 to 24.04, os this might be impacting the runs here.