Replace deprecated __hip_atomic_* builtins with __scoped_atomic_* equivalents

[srinivamd]

Summary

Replace deprecated __hip_atomic_load and __hip_atomic_compare_exchange_strong builtins in atomic.hpp with their non-deprecated equivalents __scoped_atomic_load_n and __scoped_atomic_compare_exchange, using __MEMORY_SCOPE_DEVICE instead of __HIP_MEMORY_SCOPE_AGENT.

Root cause: ROCm 7.14.0 HIP compiler deprecated the __hip_atomic_* builtins. Because MIGraphX JIT-compiles GPU kernels with -Werror,-Whip-deprecated-builtins, the deprecation warnings become hard errors, causing scatter_mul (and any other operation using atomic CAS) to fail at runtime. This is a regression from ROCm 7.13.0 (PASS) to 7.14.0 (FAIL).

Changes:

• __hip_atomic_load → __scoped_atomic_load_n
• __hip_atomic_compare_exchange_strong → __scoped_atomic_compare_exchange
• __HIP_MEMORY_SCOPE_AGENT → __MEMORY_SCOPE_DEVICE
• Added #if __has_builtin(__scoped_atomic_load_n) / #else guard for backward compatibility with ROCm 7.13.x and earlier

Fixes: ROCM-24855 — test_verify_general abort on test_scatter_elements_mul_duplicate_index

Test plan

• ctest -R test_verify_general passes on ROCm 7.14.0 (MI300/MI350)
• ctest -R test_verify_general still passes on ROCm 7.13.0 (backward compat)
• No new compiler warnings from atomic.hpp