[PR] refactor(core): lazy open positioned read handles [opendal]

["Xuanwo (via GitHub)" <gi...@apache.org>]

Xuanwo opened a new pull request, #7796:
URL: https://github.com/apache/opendal/pull/7796

   # Which issue does this PR close?
   
   N/A.
   
   # Rationale for this change
   
   The recent read refactor made `Service::read` a no-IO handle creator, but several file-backed services still opened the underlying file handle from their range read paths. That changed the intended behavior for services that can reuse a cursor-independent positioned read handle.
   
   This change moves lazy handle initialization into `PositionReader` so services only need to implement `PositionRead`. The positioned handle is opened on first use and reused for later `read_at` calls within the same reader.
   
   # What changes are included in this PR?
   
   - Extend `PositionRead` with an associated opened handle and an `open` method.
   - Cache the opened handle inside `PositionReader` with `mea::once::OnceCell`.
   - Update fs, compfs, hdfs, hdfs-native, and monoiofs to implement only `PositionRead` for positioned reads.
   - Move hdfs reads from `async_open + seek` streaming to `hdrs::File::read_at` on a reusable handle.
   
   # Are there any user-facing changes?
   
   No public API changes. This restores the intended internal behavior for reusable positioned read handles in file-backed services.
   
   # AI Usage Statement
   
   This PR was implemented with assistance from OpenAI Codex.
   
   # Validation
   
   - `cargo fmt --all`
   - `CARGO_TARGET_DIR=/tmp/opendal-a260-target-pr cargo check -p opendal-service-fs -p opendal-service-compfs -p opendal-service-hdfs -p opendal-service-hdfs-native -p opendal-service-monoiofs`
   - `CARGO_TARGET_DIR=/tmp/opendal-a260-target-pr cargo clippy -p opendal-service-fs -p opendal-service-compfs -p opendal-service-hdfs -p opendal-service-hdfs-native -p opendal-service-monoiofs --all-targets -- -D warnings`
   - `git diff --check`
   


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Re: [PR] refactor(core): lazy open positioned read handles [opendal]

["Xuanwo (via GitHub)" <gi...@apache.org>]

Xuanwo merged PR #7796:
URL: https://github.com/apache/opendal/pull/7796


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