Add type hints to `TestBase` (#10647)
Add type hints to `TestBase` (#10647)

[ci skip-rust]
pantsbuild/pants,benjyw/pants,benjyw/pants,pantsbuild/pants,pantsbuild/pants,jsirois/pants,pantsbuild/pants,benjyw/pants,jsirois/pants,benjyw/pants,benjyw/pants,benjyw/pants,pantsbuild/pants,pantsbuild/pants,benjyw/pants,pantsbuild/pants,jsirois/pants