Correctly sort dir files alphabetically to match Liberty behavior

[evie-lau]

• Use case-insensitive sort for dir files to match Liberty behavior.
• Fix configDropins processing to sort alphabetically
• Simplified and refactored some code.

Current 23.0.0.10 release has a bug where it uses case-sensitive sort for <include> dirs.
Fix in open-liberty went in recently, and will be in the 23.0.0.12 release

[cherylking]

Please build/run the tests for LMP and LGP with this branch and confirm none of the tests need updating since it is a change in behavior (even though it was a bug and incorrect behavior before). TIA

[evie-lau]

LMP/LGP builds passed with these changes included.
Used the same build commands as what runs in Github Actions

mvn -V verify --batch-mode --no-transfer-progress --errors -DtrimStackTrace=false -Ponline-its -D"invoker.streamLogsOnFailures"=true -Druntime=ol -DruntimeVersion=23.0.0.10

gradle clean install check -P"test.exclude"="**/TestSpringBootApplication30*,**/DevContainerTest*" -Druntime=ol -DruntimeVersion=23.0.0.10 --stacktrace --i