fix(storage): reclaim when a flusher waits for a clean block

[tonyalaribe]

Start a reclaim when get_clean_block has to park a waiter, and once at the end of BlockManager::init. Previously reclaim ran only after taking a clean block or finishing a write or reclaim. A device recovered with 0 clean blocks therefore parked every flusher forever and never wrote again. on_reclaim_finish already hands the reclaimed block to a waiting flusher, and reclaim_if_needed still respects clean_block_threshold and reclaim concurrency.

Add test_store_write_after_recovery_without_clean_block. It overwrites every block file with a block that holds data, reopens the store, enqueues an entry, and bounds wait() with a 10 s timeout. This needs tokio's time feature in dev-dependencies.

Validation:

• The new test fails with Elapsed without the fix and passes with it.
• cargo test -p foyer-storage: 29 lib tests passed.
• cargo fmt clean.

Fixes #1373.

[MrCroxx]

LGTM. Thank you, Anthony.

BTW, would you mind follow #1373 to pass the DCO test. 🙏 Is not necessary, but recommended.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
foyer-storage/src/engine/block/engine.rs	93.75% <100.00%> (+0.22%)	⬆️
foyer-storage/src/engine/block/manager.rs	98.20% <100.00%> (+0.01%)	⬆️

... and 2 files with indirect coverage changes

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