Reduce transient allocations in metadata encoding and partial writes

[Barre]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 95.51282% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.27%. Comparing base (f23c1e1) to head (cb88500).

Files with missing lines	Patch %	Lines
zerofs/src/nbd/server.rs	0.00%	6 Missing ⚠️
zerofs/src/fs/store/extent/read.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #633      +/-   ##
==========================================
- Coverage   83.28%   83.27%   -0.01%     
==========================================
  Files         104      104              
  Lines       47143    47167      +24     
==========================================
+ Hits        39261    39278      +17     
- Misses       7882     7889       +7     

Files with missing lines	Coverage Δ
zerofs/src/cli/debug.rs	55.72% <100.00%> (ø)
zerofs/src/cli/server.rs	25.49% <100.00%> (+0.07%)	⬆️
zerofs/src/db.rs	86.11% <100.00%> (ø)
zerofs/src/fs/boot.rs	97.85% <100.00%> (ø)
zerofs/src/fs/filter_policy.rs	100.00% <100.00%> (ø)
zerofs/src/fs/flush_coordinator.rs	91.29% <100.00%> (-0.80%)	⬇️
zerofs/src/fs/key_codec.rs	94.03% <100.00%> (-0.18%)	⬇️
zerofs/src/fs/mod.rs	94.73% <100.00%> (+0.11%)	⬆️
zerofs/src/fs/store/directory.rs	97.70% <100.00%> (ø)
zerofs/src/fs/store/extent/reclaim/cycle.rs	96.69% <100.00%> (ø)
... and 9 more

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.