At least some of the test helpers from tests/template.bats in v1.6.0 should be migrated to lib/.

These will certainly be migrated to lib/bats/helpers:

• skip_if_none_present_on_system
• git_for_windows_native_path
• create_forwarding_script

These may contain useful bits worth extracting, though migration isn't yet certain:

• assert_go_core_unpacked
• create_fake_tarball_if_not_using_real_url
• run_with_download_program