refactor: replace VecDequeue with Vec in stream_chain when applicable

[hanabi1224]

Summary of changes

Follow up on #6885 (comment)

manually tested on calibnet

❯ sha256sum forest_snapshot_calibnet_*
fde46dd2e46917ecc23781f6a05d48697bf621f026a7b4c6bc32b147bb293d6b  forest_snapshot_calibnet_2026-04-15_height_3630900.forest.car.zst.main
fde46dd2e46917ecc23781f6a05d48697bf621f026a7b4c6bc32b147bb293d6b  forest_snapshot_calibnet_2026-04-15_height_3630900.forest.car.zst.pr

Changes introduced in this pull request:

Reference issue to close (if applicable)

Closes

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

Outside contributions

• I have read and agree to the CONTRIBUTING document.
• I have read and agree to the AI Policy document. I understand that failure to comply with the guidelines will lead to rejection of the pull request.

[LesnyRumcajs]

@hanabi1224 any performance boost/drop on mainnet?

[hanabi1224]

any performance boost/drop on mainnet?

@LesnyRumcajs No difference observed on calibnet. And I won't expect a significant perf change on mainnet either. Do you need mainnet export time numbers?

[LesnyRumcajs]

any performance boost/drop on mainnet?

@LesnyRumcajs No difference observed on calibnet. And I won't expect a significant perf change on mainnet either. Do you need mainnet export time numbers?

I'd love a mainnet export timings (let's say, 3 on each branch) because calibnet often doesn't surface any issues.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.87%. Comparing base (101befd) to head (d39c68a).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

Files with missing lines	Coverage Δ
src/ipld/util.rs	53.97% <100.00%> (-1.68%)	⬇️

... and 4 files with indirect coverage changes

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[hanabi1224]

I'd love a mainnet export timings (let's say, 3 on each branch) because calibnet often doesn't surface any issues.

@LesnyRumcajs test on DO droplet (), numbers show slight(~9% actually) performance improvement

# main
➜  snaps for i in {1..3}; do time forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/null; done
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 78m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.52s user 3.12s system 0% cpu 1:17:45.49 total
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 79m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.79s user 3.24s system 0% cpu 1:19:03.02 total
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 82m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.87s user 3.29s system 0% cpu 1:21:34.21 total
  
 # PR
➜  snaps for i in {1..3}; do time forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/null; done
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 73m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.29s user 2.75s system 0% cpu 1:12:40.20 total
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 72m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.29s user 2.72s system 0% cpu 1:12:28.45 total
  Exporting v1 snapshot to ./forest_snapshot_mainnet_2026-04-15_height_5931700.forest.car.zst ... 0 B written in 74m (0 B/s)                                                                                                                    forest-cli snapshot export --format v1 -d 900 -t 5931700 --dry-run > /dev/nul  3.36s user 2.75s system 0% cpu 1:14:12.11 total

[LesnyRumcajs]

I'd love a mainnet export timings (let's say, 3 on each branch) because calibnet often doesn't surface any issues.

@LesnyRumcajs test on DO droplet (), numbers show slight(~9% actually) performance improvement

That's amazing, worth putting in the changelog. ;)