test(core-logger): unit tests for logger and manager

[faustbrian]

Proposed changes

Increased coverage for core-logger and some refactoring.

Types of changes

• Refactoring (improve a current implementation without adding a new feature or fixing a bug)
• Test (adding missing tests or fixing existing tests)

Checklist

• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes

[ghost]

The ci/circleci: test-node10-functional job is failing as of ac02742ad3ad2975b0c47880fd252051beea55a5. Please review the logs for more information.

Once you've pushed the fixes, the build will automatically re-run. Thanks!

[codecov-io]

Codecov Report

Merging #2373 into 2.4 will increase coverage by 0.07%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##              2.4    #2373      +/-   ##
==========================================
+ Coverage   68.44%   68.51%   +0.07%     
==========================================
  Files         403      403              
  Lines        8560     8564       +4     
  Branches      377      377              
==========================================
+ Hits         5859     5868       +9     
+ Misses       2658     2653       -5     
  Partials       43       43

Impacted Files	Coverage Δ
packages/core-logger-winston/src/driver.ts	85.71% <0%> (-6.6%)	⬇️
packages/core-logger/src/logger.ts	61.9% <53.84%> (+28.57%)	⬆️
packages/core-logger/src/manager.ts	100% <0%> (+18.18%)	⬆️

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