Adds debug mode for pytest unit tests

[dmitryduev]

Description

In this PR:

• Provision an admin user to use with the app when running pytest tests. Users generated per requesting test are not removed at the end of the test so that developers can inspect the app with the admin account at the end of the test session.

- Unset global wandb objects at the end of each test to improve isolation.

Testing

How was this PR tested?

Checklist

• Include reference to internal ticket "Fixes WB-NNNN" (and github issue "Fixes #NNNN" if applicable)

[codecov]

Codecov Report

Merging #4145 (5a036c7) into master (743a0a6) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4145      +/-   ##
==========================================
- Coverage   82.69%   82.61%   -0.08%     
==========================================
  Files         256      256              
  Lines       32534    32534              
==========================================
- Hits        26905    26879      -26     
- Misses       5629     5655      +26     

Flag	Coverage Δ
functest	55.01% <ø> (+0.03%)	⬆️
unittest	73.33% <ø> (-0.17%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wandb/sdk/lib/timed_input.py	44.04% <0.00%> (-14.29%)	⬇️
wandb/docker/auth.py	49.55% <0.00%> (-1.77%)	⬇️
wandb/filesync/step_prepare.py	93.67% <0.00%> (-1.27%)	⬇️
wandb/sdk/service/service.py	89.15% <0.00%> (-1.21%)	⬇️
wandb/sdk/data_types/base_types/media.py	92.08% <0.00%> (-0.72%)	⬇️
wandb/sdk/internal/internal_api.py	86.46% <0.00%> (-0.52%)	⬇️
wandb/sdk/wandb_setup.py	88.44% <0.00%> (-0.51%)	⬇️
wandb/sdk/wandb_settings.py	94.56% <0.00%> (-0.28%)	⬇️
wandb/sdk/wandb_run.py	90.92% <0.00%> (-0.25%)	⬇️
wandb/apis/public.py	82.25% <0.00%> (-0.20%)	⬇️
... and 5 more