[Store] Structure ShmSpdkRegistrationConfig environment settings

[bitborne]

Description

Part of #3809. Extract MC_STORE_REGISTER_SPDK from shm_helper.cpp into a private, client-owned ShmSpdkRegistrationConfig and the common environment catalog. ShmHelper still reads the flag once during singleton construction, and only the exact value 1 enables registration; unset, empty, and other values remain disabled. The hugepage and SPDK registration behavior is otherwise unchanged.

The raw string preserves the original strict comparison rather than adopting a generic boolean parser. This follows the single-owner configuration boundary of merged #4165 and #4166 and complements the existing registration feature in merged #3717. Open #4179 moves the client source layout without migrating this flag; integration conflicts can be addressed if it merges first.

Module

• Mooncake Store (mooncake-store)
• Common (mooncake-common)

Type of Change

• Refactor

How Has This Been Tested?

Test commands:

cmake --build build/config-check --target shm_spdk_registration_config_test --parallel 231
ctest --test-dir build/config-check -R '^shm_spdk_registration_config_test$' --output-on-failure
./scripts/code_format.sh --check --staged
pre-commit run --files mooncake-common/include/environment_variables.h mooncake-store/src/CMakeLists.txt mooncake-store/src/config/shm_spdk_registration_config.cpp mooncake-store/src/config/shm_spdk_registration_config.h mooncake-store/src/shm_helper.cpp mooncake-store/tests/CMakeLists.txt mooncake-store/tests/shm_spdk_registration_config_test.cpp

Test results:

• Unit tests pass for the new shared-memory SPDK registration configuration.
• Integration tests pass (if applicable)
• Manual testing done (describe below)

The new test first failed for MC_STORE_REGISTER_SPDK=1 with the default-only implementation and passed after the configuration extraction.

Checklist

• I have performed a self-review of my own code
• I have formatted my code using ./scripts/code_format.sh
• I have run pre-commit on the files changed in this PR and all hooks pass
• I have updated the documentation (if applicable)
• I have added tests to prove my changes are effective
• For changes >500 LOC: I have filed an RFC issue

No documentation change: the existing strict opt-in behavior is unchanged.

AI Assistance Disclosure

• No AI tools were used
• AI tools were used (specify below)

Codex assisted with ownership analysis, implementation, focused RED-to-GREEN tests, and review. The human submitter will review every changed line and is responsible for the change end to end.