Security Fixes: Critical bug fixes and improved test coverage

[viordash]

This PR addresses several critical security and stability issues discovered during code review of the MigrateAnyData library. All fixes include regression tests where applicable.

Key Changes

1. Memory Safety Improvements

Remove dead NULL checks after new operator

• Standard C++ new throws std::bad_alloc, never returns NULL
• Removed misleading checks that created false sense of security

Prevent integer overflow in buffer size calculation

• Changed int to size_t for size calculations
• Added overflow check before memory allocation

Key files: MigrateAnyData/MigrateAnyData.cpp

2. Input Validation

Add zero division check for stored record size

• Prevents crash when GetSizeOfCurrentData() returns 0

Add null checks for function pointers

• Validates MigrateUp, MigrateDown, and onMigrateDataItem before invocation

Key files: MigrateAnyData/MigrateAnyData.cpp

3. String Safety

Ensure null-termination in string field migration macros

• strncpy doesn't guarantee null-termination when source is longer than buffer
• Added explicit null-terminator assignment

Key files: MigrateAnyData/MigrateAnyData.h

4. Tests

Added 3 new test cases:

• TestError_Zero_Record_Size - validates zero size handling
• TestError_Null_Migrate_Function - validates null function pointer handling
• TestString_Field_Null_Termination - validates string macro safety

Key files: Tests/Error_Zero_Record_Size.cpp, Tests/Error_Null_Migrate_Function.cpp, Tests/String_Field_Null_Termination.cpp, CMakeLists.txt

5. CI Improvement

Added --output-on-failure to ctest for better debugging in CI.

Key files: .github/workflows/cmake-multi-platform.yml