Maintenance: add tests for child logger attributes

[saragerion]

Description of the feature request

Problem statement

During a 1:1 feedback session it emerged that the current behavior of Logger.createChild might not be immediately clear to people approaching the library for the first time. Likewise, the current unit test cases, while reaching 100% coverage, might use some improvements to cover all cases.

The steps to complete this issue should be (in this order):

• Assess the current implementation of both feature and tests
• Compare the implementation with current documentation section
• Report findings / proposed improvements (under this issue). The report should cover: 1/ are current unit tests covering all cases? If not, which cases could be added? 2/ does current documentation articulate clearly the behavior of createChild? If not, what would you add?
• Implement any changes that might have emerged from point above

Summary of the feature

N/A

Code examples

Unit tests for the feature: link
Implementation for the feature: link

Benefits for you and the wider AWS community

Describe alternatives you've considered

Additional context

N/A

Related issues, RFCs

N/A