Move to hatch for build tooling

[emmyoop]

Resolves #12151

Problem

dbt-core used setuptools as its build backend while dbt-adapters and dbt-common use hatch, creating inconsistency across the dbt ecosystem. This complicated build processes, required maintaining legacy build files, and created build isolation issues (#10465) where wheels and source distributions weren't built in separate environments.

Solution

Build System Migration

• Migrated to hatchling as the build backend with declarative configuration in pyproject.toml
• Created custom build hook to handle LICENSE file requirements for both GitHub (repo root) and PyPI (package root)
• Established core/dbt/__version__.py as single source of truth for versioning

Legacy Cleanup

• Removed MANIFEST.in (package contents now defined declaratively)
• Simplified setup.py to minimal compatibility shim for backwards compatibility
• Updated build script to use hatch build instead of python -m build

CI/CD Updates

• Migrated all GitHub Actions workflows to use hatch commands for setup, testing, linting, and building
• Updated release workflows to use hatch for version management and distribution building
• Updated version detection in release branch workflows to read from new version location

Developer Experience

• Updated contributor documentation with hatch installation and usage instructions
• Defined hatch environments and scripts for common development tasks (testing, linting, building)
• Streamlined setup process with hatch run setup

Build Isolation

• Separate hatch environments for building wheels vs source distributions
• Separate hatch environments for running tests vs checking distributions
• Addresses build isolation concerns from Build and check source distributions and wheels independently in build packages #10465

Checklist

• I have read the contributing guide and understand what's expected of me.
• I have run this code in development, and it appears to resolve the stated issue.
• This PR includes tests, or tests are not required or relevant for this PR.
• This PR has no interface changes (e.g., macros, CLI, logs, JSON artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX.
• This PR includes type annotations for new and modified functions.

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 15.38462% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.97%. Comparing base (1219bd4) to head (f6d2070).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12192      +/-   ##
==========================================
- Coverage   91.98%   91.97%   -0.01%     
==========================================
  Files         203      205       +2     
  Lines       24965    24967       +2     
==========================================
  Hits        22964    22964              
- Misses       2001     2003       +2     

Flag	Coverage Δ
integration	88.86% <15.38%> (-0.01%)	⬇️
unit	65.18% <15.38%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
Unit Tests	65.18% <15.38%> (-0.01%)	⬇️
Integration Tests	88.86% <15.38%> (-0.01%)	⬇️

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