Factories for test data

[sfc-gh-pjafari]

Pre-review checklist

• I've confirmed that instructions included in README.md are still correct after my changes in the codebase.
• I've added or updated automated unit tests to verify correctness of my new code.
• N/A - I've added or updated integration tests to verify correctness of my new code.~
• I've confirmed that my changes are working by executing CLI's commands manually on MacOS.
• I've confirmed that my changes are working by executing CLI's commands manually on Windows.
• I've confirmed that my changes are up-to-date with the target branch.
• N/A - I've described my changes in the release notes.~
• I've described my changes in the section below.

Changes description

Goal: Declarative way of creating test-data, to ultimately serve as a replacement for making more files and folders under tests/test-data/projects.
Changes:

• Factory to create a PDF file (snowflake.yml and snowflake.local.yml for V1.*) with specified properties (look at this updated test for an example).

• Same factory above can return a yml dict or a string of the PDF, without writing to disk, using the build method. Look at this updated test for the usage example

• Project Factory that can create PDF file with the specified properties, as well as other files with specified content. See use_integration_project for an example setup that recreates tests/test-data/projects/integration

TODO after this POC

• Pdfv2
• Capability to update files, useful for integration test cases
• Add utils/fixtures for some frequent presets
• manifest factory