[phase 2] Update all unit tests to use new API naming conventions

[aregtech]

Important

Refactoring changes should be rebased and merged against this branch:
feature/655-api-modernization-and-refactoring

Summary

Update all unit tests to use the new naming conventions.

Scope

18 test files under tests/units/:

• DateTimeTest.cpp
• FileTest.cpp
• NEStringTest.cpp
• StringUtilsTest.cpp
• TEArrayListTest.cpp
• TEFixedArrayTest.cpp
• TEHashMapTest.cpp
• TELinkedListTest.cpp
• TEMapTest.cpp
• TEPropertyTest.cpp
• TERingStackTest.cpp
• TESortedLinkedListTest.cpp
• TEStackTest.cpp
• LogScopesTest.cpp
• OptionParserTest.cpp
• GUnitTest.hpp
• UnitTestUtilities.hpp
• CMakeLists.txt

What changes

• All #include paths updated
• All method calls converted to snake_case
• All type names updated (e.g., TEArrayList → ArrayList)
• Test file names renamed to match new class names (e.g., TEArrayListTest.cpp → ArrayListTest.cpp)
• CMakeLists.txt updated for renamed files

Depends on

• Framework renaming must be complete (at least areg/base/ module)

Acceptance criteria

• All unit tests compile
• All unit tests pass (ctest or gtest runner)
• Test names reflect new class names
• No old naming conventions remain in test code