SDSTOR-20656: clear wbc chunk selector

[nnastonen]

0. Create homestore with chunk selector
1. Create btree1 and populate it
2. Nodes get into wbc cache
3. Destroy btree1 (wbc purge is not done, also volume's chunk bitmap is not cleared)
4. Create btree2 and populate it
5. Nodes get into wbc cache and we get cache corruption, duplicate inserts

This change makes chunk release asynchronous and defers returning the chunk to the free pool until cleanup is complete.

New flow:

• detach the volume's chunk list from m_volume_chunks
• run asynchronous cleanup for all the chunks
• in cleanup, evict all allocated blkids for the chunks from WBC
• [reset the chunks' block allocator state (bitmap)]
• reinsert the chunks into m_per_dev_chunks

This PR also addresses this ticket SDSTOR-20651

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 52.57143% with 83 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (dev/v6.x@d2e0087). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/lib/volume/volume_chunk_selector.cpp	52.00%	19 Missing and 53 partials ⚠️
src/lib/homeblks_impl.cpp	37.50%	3 Missing and 7 partials ⚠️
src/lib/volume/volume.cpp	66.66%	0 Missing and 1 partial ⚠️
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Additional details and impacted files

@@             Coverage Diff             @@
##             dev/v6.x     #179   +/-   ##
===========================================
  Coverage            ?   49.92%           
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  Files               ?       19           
  Lines               ?     1338           
  Branches            ?      588           
===========================================
  Hits                ?      668           
  Misses              ?      275           
  Partials            ?      395           

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[Copilot]

Copilot review overview

🟡 Changes recommended

Resize races, destruction ordering, and FlatBuffers field placement can cause crashes or compatibility failures.

Review effort: Balanced
Findings: 3 · 1 · 1

Open (5)

• Inserted FlatBuffers field breaks schema compatibility · New
• Non-atomic capacity check can crash concurrent resize · New
• Volume destruction races with resize worker cleanup · New
• Early return bypasses low-space resize policy · New
• Tests omit asynchronous WBC cleanup and safe reuse · New

What changed in this PR

Introduces asynchronous chunk cleanup to prevent WBC corruption when destroyed-volume chunks are reused, alongside configurable lazy allocation.

Changes:

• Quiesces selection/resizing before WBC eviction, allocator reset, and chunk reuse.
• Adds dynamic chunk-allocation configuration and CLI override.
• Expands concurrency tests and bumps the package version.

File	Description
README.md	Documents the allocation CLI option.
conanfile.py	Bumps version to 6.0.11.
src/​lib/​home_blks_config.fbs	Adds the allocation setting.
src/​lib/​homeblks_impl.cpp	Resolves CLI/config allocation behavior.
src/​lib/​homeblks_impl.hpp	Declares the configuration accessor.
src/​lib/​volume/​volume.cpp	Applies allocation configuration to volumes.
src/​lib/​volume/​volume_chunk_selector.cpp	Implements synchronized resizing and asynchronous cleanup.
src/​lib/​volume/​volume_chunk_selector.hpp	Adds per-volume concurrency state.
src/​lib/​volume/​tests/​test_common.hpp	Defines the test option default.
src/​lib/​volume/​tests/​test_volume_chunk_selector.cpp	Adds concurrency and reuse tests.
src/​test/​legacy_ublk/​homeblk_ublk_cli.cpp	Exposes the CLI override.

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[shosseinimotlagh]

LGTM

[JacksonYao287]

@nnastonen thanks for this PR, I am not quite familiar with homeblks, so just left a concern here.

pls correct me if I am wrong