Parallelize tests

[kmontemayor2-sc]

Our tests all run sequentially, this is very slow.

We should try to parallelize them.

NOTE: We do have this flag

GiGL/python/gigl/common/utils/test_utils.py

Line 66 in 4f7b05b

start_dir: LocalUri, pattern: str, use_sequential_execution: bool = False

but it doesn't really speed things up...