Replace config context managers with pytest fixtures

[jenshnielsen]

Extracted from #4763

• Using fixtures avoids the patterns of tests that are completely within a context manger improving readability
• Since the context mangers cooperate, we avoid the logic of having to patch config objects within the test

[codecov]

Codecov Report

Merging #4764 (2101279) into master (ad5821c) will decrease coverage by 0.92%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4764      +/-   ##
==========================================
- Coverage   68.19%   67.27%   -0.93%     
==========================================
  Files         339      339              
  Lines       32003    32003              
==========================================
- Hits        21826    21530     -296     
- Misses      10177    10473     +296