fix: hold runtime ref and handle to prevent spawn after shutdown

[MrCroxx]

What's changed and what's your intention?

Please explain IN DETAIL what the changes are in this PR and why they are needed. :D

As title.

Checklist

• I have written the necessary rustdoc comments
• I have added the necessary unit tests and integration tests
• I have passed make all (or make fast instead if the old tests are not modified) in my local environment.

Related issues or PRs (optional)

fix #735

[codecov]

Codecov Report

Attention: Patch coverage is 93.97590% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
foyer-storage/src/store.rs	66.66%	6 Missing ⚠️
foyer-memory/src/generic.rs	87.50%	1 Missing ⚠️
foyer-storage/src/device/direct_fs.rs	85.71%	1 Missing ⚠️
foyer-storage/src/device/mod.rs	66.66%	1 Missing ⚠️
foyer-storage/src/large/generic.rs	96.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
foyer-common/src/asyncify.rs	50.00% <100.00%> (ø)
foyer-common/src/runtime.rs	84.21% <100.00%> (+12.78%)	⬆️
foyer-memory/src/cache.rs	86.18% <100.00%> (ø)
foyer-storage/src/device/direct_file.rs	84.91% <100.00%> (-0.17%)	⬇️
foyer-storage/src/device/monitor.rs	78.64% <100.00%> (ø)
foyer-storage/src/large/flusher.rs	85.14% <100.00%> (ø)
foyer-storage/src/large/reclaimer.rs	85.48% <100.00%> (ø)
foyer-storage/src/large/recover.rs	90.29% <100.00%> (ø)
foyer-storage/src/large/scanner.rs	75.70% <100.00%> (-0.02%)	⬇️
foyer-storage/src/large/tombstone.rs	96.55% <100.00%> (+0.08%)	⬆️
... and 7 more

[MrCroxx]

Wait for risingwavelabs/risingwave#18652 to pass.

[MrCroxx]

This PR fixed the bug. But there is performance regression. Let me check why.

[MrCroxx]

Make it back to normal. It is because the disk io was not using dedicated foyer runtime, which is a bug. After this PR fixed it, the --read/write--runtime-max-blocking-thread works and limited the threads count to a low number and limited the performance. After removing the option from foyer-bench, the performance looks fine.

[MrCroxx]

The new benchmark command:

cargo build --release --features jemalloc && PATH=/home/mrcroxx/.local/bin:$PATH RUST_BACKTRACE=1 RUST_LOG=info flamegraph -- ./target/release/foyer-bench --file /dev/nvme2n1 --mem 64MiB --disk 100GiB --region-size 64MiB --get-range 100000 --flushers 4 --reclaimers 4 --time 60 --writers 256 --w-rate 4MiB --admission-rate-limit 500MiB --readers 32 --r-rate 32MiB --metrics --warm-up 2 --runtime separated --user-runtime-worker-threads 8 --read-runtime-worker-threads 8 --write-runtime-worker-threads 4