[Enhancement✨] Gate CommitLog prefetch import for Linux clippy

[mxsm]

Current Behavior

PR #7760 (build(deps): bump indicatif from 0.18.5 to 0.18.6) fails the GitHub Actions RocketMQ Rust CI / Check (fmt + clippy) job.

The failing command is:

cargo clippy --workspace --no-deps --all-targets --all-features -- -D warnings

The CI log reports an unused import in rocketmq-store/src/log_file/commit_log_loader.rs:

error: unused import: `crate::utils::ffi::prefetch_virtual_memory`
  --> rocketmq-store/src/log_file/commit_log_loader.rs:38:5
  = note: `-D unused-imports` implied by `-D warnings`

The import is only needed by the Windows PrefetchVirtualMemory path, while the failing CI job runs on Linux.

Proposed Enhancement

Gate the prefetch_virtual_memory import with the same Windows-only cfg boundary as the call site in CommitLogLoader::apply_file_prefetch.

This keeps the Windows recovery file prefetch behavior intact while preventing Linux/Unix clippy from seeing an unused Windows-only import.

Benefits

• Restores the root workspace clippy gate for Linux CI.
• Keeps the CommitLog recovery prefetch implementation platform-specific and explicit.
• Unblocks dependency update PRs such as build(deps): bump indicatif from 0.18.5 to 0.18.6 #7760 that otherwise fail on unrelated lint noise.

Additional Context

Observed failing job: https://github.com/mxsm/rocketmq-rust/actions/runs/28551274313/job/84648782240?pr=7760

Local validation performed for the fix:

cargo fmt --all
cargo clippy -p rocketmq-store --no-deps --all-targets --all-features -- -D warnings
cargo clippy --workspace --no-deps --all-targets --all-features -- -D warnings

An additional Linux target clippy attempt was blocked locally by the missing x86_64-linux-gnu-gcc cross compiler required by native build dependencies.