refactor: replaced 'os.path.join()' uses with 'pathlib.Path' / syntax

[soto-raul]

Description

This PR closes #1627.
As per the issue's description, in this PR most instances of os.path.join on strings with the corresponding / syntax for pathlib.Path objects. For example:

# BEFORE
full_path = os.path.join(root_dir, dir_path)

# AFTER
full_path = Path(root_dir) / dir_path # After

However, files with the prefix test_ were not considered for this refactor; therefore, they maintained the usage of os.path.join

Files Changed

• install/find_mpi.py
• libensemble/executors/executor.py
• libensemble/manager.py
• libensemble/resources/resources.py
• libensemble/tests/run_tests.py
• libensemble/tests/scaling_tests/forces/forces_adv/forces_simf.py
• libensemble/tests/scaling_tests/forces/forces_adv/forces_support.py
• libensemble/tests/scaling_tests/forces/forces_adv/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/forces_adv/run_libe_forces_from_yaml.py
• libensemble/tests/scaling_tests/forces/forces_gpu/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/forces_gpu_var_resources/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/forces_multi_app/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/forces_simple/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/forces_simple_with_input_file/run_libe_forces.py
• libensemble/tests/scaling_tests/forces/globus_compute_forces/forces_simf.py
• libensemble/tools/parse_args.py
• libensemble/tools/tools.py

Additional Notes

It would be a good idea to consider replacing other uses of the os module with their pathlib equivalents. For example, os.path.exists() could be replaced by Path.exists().

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.29%. Comparing base (a7382ff) to head (98a9fce).
⚠️ Report is 1 commits behind head on develop.

❗ There is a different number of reports uploaded between BASE (a7382ff) and HEAD (98a9fce). Click for more details.

HEAD has 12 uploads less than BASE

Flag	BASE (a7382ff)	HEAD (98a9fce)
	22	10

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #1637       +/-   ##
============================================
- Coverage    93.29%   78.29%   -15.00%     
============================================
  Files           81       81               
  Lines         8188     8192        +4     
  Branches      1257     1257               
============================================
- Hits          7639     6414     -1225     
- Misses         358     1545     +1187     
- Partials       191      233       +42     

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[jlnav]

@soto-raul We just merged some changes into the target branch that conflict with your PR. If possible please resolve these conflicts, then if tests pass we'll be happy to merge.