feat(services/smb): add smb service

[suyanhanx]

Which issue does this PR close?

Closes #7369.

Rationale for this change

OpenDAL does not have first-class SMB support today. This change adds an SMB service backed by smb-rs so Operator::from_uri and the service registry can open SMB shares via smb://host/share/root.

This draft is intentionally split from the dependency fix path. OpenDAL is not carrying a local fork of smb-rs; the upstream async-read fix is proposed separately in afiffon/smb-rs#167.

What changes are included in this PR?

• add a new core/services/smb service crate
• wire services-smb into the workspace feature list and registry exports
• support create_dir, stat, read, write, delete, and list
• parse SMB URIs as smb://host/share/root and add matching .env.example entries
• keep OpenDAL-style slash paths internally and only convert to SMB separators at the UncPath boundary
• explicitly close SMB resources in stat/list/create/delete flows to avoid async destructor issues
• treat transient DELETE_PENDING / not-found races during list and delete as skips instead of hard failures

This draft does not enable copy or rename yet.

Are there any user-facing changes?

Yes. Users get a new services-smb feature and can configure SMB tests via:

• OPENDAL_SMB_ENDPOINT
• OPENDAL_SMB_SHARE
• OPENDAL_SMB_ROOT
• OPENDAL_SMB_USER
• OPENDAL_SMB_PASSWORD

Validation run on this branch:

• cargo test -p opendal-service-smb
• cargo check -p opendal --features services-smb
• cargo clippy -p opendal-service-smb --all-targets -- -D warnings
• cargo clippy -p opendal --all-targets --features services-smb -- -D warnings
• OPENDAL_TEST=smb OPENDAL_SMB_ENDPOINT=127.0.0.1:1445 OPENDAL_SMB_SHARE=MyShare OPENDAL_SMB_ROOT=/ OPENDAL_SMB_USER=alice OPENDAL_SMB_PASSWORD=alipass cargo test -p opendal --features tests,services-smb behavior

One dependency caveat remains: with crates.io smb = 0.11.1, large reads can still log Async command is not allowed in this context before OpenDAL retries them successfully. That fix is under review upstream in afiffon/smb-rs#167.

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