fix(test): resolve id_t ambiguity in test_shm.cpp

- Remove 'using namespace ipc::shm;' to avoid id_t conflict with system id_t
- Add explicit shm:: namespace prefix to all shm types and functions
- Apply to: id_t, handle, acquire, get_mem, release, remove, get_ref, sub_ref
- Apply to: create and open constants
- Fix comments to avoid incorrect namespace references
- Resolves compilation error: 'reference to id_t is ambiguous'

Author: mutouyun