bugfix/issue-466-py-test-resolutions-dx

[njlr]

Closes #466

• Make resolutions consistent between py_binary and py_test
• Allow a list to be passed to from_requirements
• Add an example of virtual_deps feature

---

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): no
• Suggested release notes appear below:

• Fix: Make resolutions consistent between py_binary and py_test
• Feature: Allow a list to be passed to from_requirements
• Docs: Add an example of virtual_deps feature

Test plan

• Manual testing; please provide instructions so we can reproduce: Added an example