feat(binding/go): add deleter

[ryankert01]

Which issue does this PR close?

N/A

Rationale for this change

Core exposes Operator::deleter(), which queues paths and uses the service's batch deletion. Neither binding exposed it, so Go users deleted one path per request.

What changes are included in this PR?

// Delete a known set of paths.
err := op.Remove([]string{"a.txt", "b.txt", "c.txt"})

// Or drive a Deleter to queue paths as you discover them.
deleter, err := op.Deleter()
for _, path := range paths {
    err = deleter.Delete(path) // queues only
}
err = deleter.Close() // flushes the queue, waits, reports the outcome

• C: opendal_operator_deleter returns an opendal_deleter handle, driven by opendal_deleter_delete, _delete_with, _close and _free.
• C: opendal_delete_options gains a From impl for options::DeleteOptions, now shared with opendal_operator_delete_with.
• Go: Operator.Deleter returns a Deleter with Delete(path, opts...) and Close. Delete queues a path; Close flushes the queue and reports the outcome. Operator.Remove(paths) wraps it.
• Behavior tests, FFI ownership tests, and a "Delete many paths" docs section.

Are there any user-facing changes?

New Operator.Deleter and Operator.Remove in the Go binding, plus the opendal_operator_deleter and opendal_deleter_* C functions. No breaking changes; docs updated.

AI Usage Statement

Claude Code with Opus 5. (I understand the code that I told claude to write)

[ryankert01]

cc @dentiny

[dentiny]

current implementation seems to iterate on the given paths, which goes across the FFI boundary and block_on its completion, I'm wondering if it's better to expose a bulk delete API?