rs_port: UB stopgap fixes for future/pointer (#618)

[Rahul-2k4]

Description

Summary of changes:

• Avoid ownership-taking Box::from_raw in Debug implementations of
  MetaCallFuture and MetaCallPointer.
• Add null guards before destructive raw-pointer drop/destroy paths.
• Make MetaCallPointer::clone deep-clone Rust-side boxed value storage to
  avoid clone-based double-free.
• Added regression tests for:
  • debug_on_null_raw_future_does_not_take_ownership
  • clone_and_consume_value_does_not_share_owned_box

Fixes #618

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have performed a self-review of my own code.
• My changes generate no new warnings.
• I have added tests/screenshots (if any) that prove my fix is effective or that my feature works.
• I have tested the tests implicated (if any) by my own code and they pass (make test or ctest -VV -R <test-name>).
• If my change is significant or breaking, I have passed all tests with ./docker-compose.sh test &> output and attached the output.
• I have tested my code with OPTION_BUILD_ADDRESS_SANITIZER or ./docker-compose.sh test-address-sanitizer &> output and OPTION_TEST_MEMORYCHECK.
• I have tested my code with OPTION_BUILD_THREAD_SANITIZER or ./docker-compose.sh test-thread-sanitizer &> output.
• I have tested with Helgrind in case my code works with threading.
• I have run make clang-format in order to format my code and my code follows the style guidelines.

Additional verification:

• Offline ASAN build/install passed:
  • cmake -B build-asan-offline ... -DOPTION_BUILD_ADDRESS_SANITIZER=On
  • cmake --build build-asan-offline --target install -j
• Offline TSAN build/install passed:
  • cmake -B build-tsan-offline ... -DOPTION_BUILD_THREAD_SANITIZER=On
  • cmake --build build-tsan-offline --target install -j