feat(sweeps): Sweep scheduler cleanup and better tests

[hu-po]

Fixes WB-10588

Description

Cleans up some of the threading logic in the sweep scheduler. Adds better unit tests for sweep scheduler.

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 #4100 (730c7b5) into master (9053171) will increase coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 730c7b5 differs from pull request most recent head cbfc4b1. Consider uploading reports for the commit cbfc4b1 to get more accurate results

@@            Coverage Diff             @@
##           master    #4100      +/-   ##
==========================================
+ Coverage   82.61%   82.63%   +0.01%     
==========================================
  Files         255      255              
  Lines       32370    32349      -21     
==========================================
- Hits        26741    26730      -11     
+ Misses       5629     5619      -10     

Flag	Coverage Δ
functest	54.81% <0.00%> (+0.07%)	⬆️
unittest	73.34% <100.00%> (-0.03%)	⬇️

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

Impacted Files	Coverage Δ
wandb/sdk/launch/sweeps/scheduler.py	100.00% <100.00%> (+2.87%)	⬆️
wandb/sdk/launch/sweeps/scheduler_sweep.py	98.75% <100.00%> (-1.25%)	⬇️
wandb/integration/tensorboard/monkeypatch.py	90.12% <0.00%> (-2.47%)	⬇️
wandb/sdk/lib/git.py	79.01% <0.00%> (ø)
wandb/sdk/internal/internal_api.py	86.50% <0.00%> (+0.12%)	⬆️
wandb/filesync/step_prepare.py	94.93% <0.00%> (+1.26%)	⬆️
wandb/sdk/lib/sock_client.py	91.36% <0.00%> (+1.43%)	⬆️
wandb/sdk/internal/meta.py	90.79% <0.00%> (+3.06%)	⬆️

[KyleGoyette]

LGTM, but there are some questions that I think warrant discussion