refactor: Extract Flow<DataClass> tests to FlowDataClassTest, remove 739 redundant tests

CalculatorTest.kt contained 769 tests, 739 of which were exact duplicates of
tests in 13 specialized test files (CoreTest, EnumTest, ObjectTest, etc.).

Extracted the 30 unique 'flow dc - *' tests (Flow with data classes) into
FlowDataClassTest.kt and removed the monolithic CalculatorTest.kt to reduce
redundancy and improve test organization.

Author: kdroidFilter