test: fix integration tests

[Dniskk]

Fix integration tests

Changes

• Convert pyproject.toml to pyproject.toml.in templates with configurable hatch-dotenv package requirement
• Add run_tests_no_cache_clear.sh for CI environments with fresh hatch installations
• Update run_tests_hatch_pip.sh and run_tests_hatch_pipx.sh to generate pyproject.toml from templates
• Simplify run-integration-tests action to use the new script with a configurable package input
• Add integration tests to PR workflow using local package (hatch-dotenv @ file://...)
• Release workflow continues to test against PyPI version

Files

• .github/actions/run-integration-tests/action.yml - accepts package input, defaults to PyPI
• .github/workflows/pr.yml - adds integration tests job with local package
• integration_tests/*.sh - scripts accept package requirement as argument
• integration_tests/*/pyproject.toml.in - templates with {{HATCH_DOTENV_PACKAGE}} placeholder