[python] Allow `obs_query=None`/`var_query=None` in `ExperimentAxisQu… #526

Job	Run time
ubuntu-22.04 setuptools	4m 58s
docker TILEDB_EXISTS: no TILEDBSOMA_EXISTS: no	4m 41s
macos TILEDB_EXISTS: no TILEDBSOMA_EXISTS: no	6m 18s
macos-12 setuptools	9m 40s
macos TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: no	7m 32s
macos TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: yes	7m 31s
docker TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: no	4m 59s
docker TILEDB_EXISTS: yes TILEDBSOMA_EXISTS: yes	4m 36s
	50m 15s

Provide feedback