Makes parameters of str type case-insensitive

[jaehyi-aws]

Issue #, if available:

Description of changes:

Updates to get_yesno_parameter function:

1. Adds type hints to function parameters
2. Attempts to simplify the logic within the function
3. Uses identity comparison ( is ) in place of equality ( == ) with None
4. Converts the default value (once it is a str type) to lowercase within the function, ensuring case-insensitive comparison regardless of how the default is specified.

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