use `Path().parent` instead of dirname in runconfig.py

[scottstanie]

Changing the only place where dirname is used directly on a string passed by the user, rather than something we construct.

os.path.dirname fails in the s1reader's orbit-getter if you pass just the name of a file in the current directory without ./ in front.

from pathlib import Path
import os

orbit_file = 'S1A_OPER_AUX_POEORB_OPOD_20220802T081843_V20220712T225942_20220714T005942.EOF'
os.path.exists(orbit_file)
# True
os.path.isdir(os.path.dirname(orbit_file))
# False

which leads to an error

Traceback (most recent call last):
  File "/u/aurora-r0/staniewi/miniconda3/envs/mapping/lib/python3.10/site-packages/ipdb/__main__.py", line 305, in main
    pdb._runscript(mainpyfile)
  File "/u/aurora-r0/staniewi/miniconda3/envs/mapping/lib/python3.10/pdb.py", line 1586, in _runscript
    self.run(statement)
  File "/u/aurora-r0/staniewi/miniconda3/envs/mapping/lib/python3.10/bdb.py", line 597, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "/u/aurora-r0/staniewi/miniconda3/envs/mapping/bin/s1_cslc.py", line 8, in <module>
    sys.exit(main())
  File "/u/aurora-r0/staniewi/repos/COMPASS/src/compass/s1_cslc.py", line 49, in main
    run(parser.run_config_path, parser.args.grid_type)
  File "/u/aurora-r0/staniewi/repos/COMPASS/src/compass/s1_cslc.py", line 40, in run
    cfg = GeoRunConfig.load_from_yaml(run_config_path, 's1_cslc_geo')
  File "/u/aurora-r0/staniewi/repos/COMPASS/src/compass/utils/geo_runconfig.py", line 70, in load_from_yaml
    bursts = runconfig_to_bursts(sns)
  File "/u/aurora-r0/staniewi/repos/COMPASS/src/compass/utils/runconfig.py", line 164, in runconfig_to_bursts
    orbit_path = get_orbit_file_from_dir(
  File "/u/aurora-r0/staniewi/repos/s1-reader/src/s1reader/s1_orbit.py", line 249, in get_orbit_file_from_dir
    raise NotADirectoryError(f"{orbit_dir} not found")
NotADirectoryError:  not found

But if you use pathlib, it works fine.

os.path.isdir(Path(orbit_file).parent)
True