chore: release 0.15.3

[suchapalaver]

Summary

• Bump crate version to 0.15.3
• Move the range-first chunked log scan APIs from Unreleased into the 0.15.3 changelog section

Verification

• cargo fmt
• git diff --check
• nix shell nixpkgs#stdenv.cc -c cargo publish --dry-run --allow-dirty