Avoid freeing failed VMM grow reservations

[fallintoplace]

Summary

• Split the VMM grow adjacent-reservation fallback into failed-reservation and noncontiguous-reservation cases.
• Only call cuMemAddressFree when cuMemAddressReserve succeeded and returned a noncontiguous address.
• Add regression coverage for both fallback paths.

Why

The previous grow path called cuMemAddressFree(new_ptr, ...) even when the adjacent cuMemAddressReserve call failed with a recoverable error. In that case the returned pointer is not an owned reservation, so cleanup can turn a recoverable fallback into another driver error.

Checks

• python3 -m py_compile cuda_core/cuda/core/_memory/_virtual_memory_resource.py cuda_core/tests/test_memory.py
• git diff --check -- cuda_core/cuda/core/_memory/_virtual_memory_resource.py cuda_core/tests/test_memory.py

Not run locally:

• uv run --no-project --with pytest --with cuda-bindings --with cuda-pathfinder --with numpy python -m pytest cuda_core/tests/test_memory.py -k 'vmm_allocator_grow_allocation_does_not_free_failed_adjacent_reservation or vmm_allocator_grow_allocation_frees_noncontiguous_adjacent_reservation'

The isolated test environment on this macOS arm64 host cannot resolve cuda-bindings, because published wheels are available for Linux and Windows but not this platform.

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