add asp commands

[nickpoindexter]

Summary

Adds first-class driver support for Atlas Stream Processing (ASP), implementing the ASP driver spec. Today users have to drop down to Database::run_command against a workspace endpoint; this PR adds a dedicated client/handles/operations layer.

What's new

Public module (driver/src/stream_processing.rs, driver/src/stream_processing/)

• StreamProcessingClient — workspace-scoped client distinct from Client. Validates the workspace URI (atlas-stream-*.<region>.a.query.mongodb.net and the .mongodb-<env>.net staging variants), enforces TLS, defaults authSource=admin. Constructor pair: with_uri_str and with_options. Static is_workspace_uri(&str) -> bool is exposed for callers that want to gate before connecting.
• StreamProcessors — create() / get() / get_info() for managing processors in a workspace.
• StreamProcessor — start() / stop() / drop() / stats() / samples() for a named processor.
• StreamProcessorInfo — typed deserialization target for getStreamProcessor. Fields the spec marks as Optional (e.g. id, pipeline_version) are Option<T>.
• StreamProcessorSamples — result of samples(), exposes cursor_id, documents, is_exhausted(). - Options: CreateStreamProcessorOptions, StartStreamProcessorOptions, FailoverOptions, GetStreamProcessorStatsOptions, GetStreamProcessorSamplesOptions. All #[derive(TypedBuilder, Serialize, Deserialize)] with #[skip_serializing_none] to match the rest of the driver's options pattern.

Operation layer (driver/src/operation/stream_processing/)
One OperationWithDefaults impl per wire command: createStreamProcessor, startStreamProcessor, stopStreamProcessor, dropStreamProcessor, getStreamProcessor, getStreamProcessorStats, startSampleStreamProcessor, getMoreSampleStreamProcessor. All target the admin database via OperationTarget::admin(client). Retryable reads (getStreamProcessor, getStreamProcessorStats) declare
Retryability::read(options) per the spec's retryability matrix.

Notable spec / server alignment

• startAfter (in StartStreamProcessorOptions) is intentionally not exposed — the spec marks it RESERVED for future use and explicitly forbids drivers from sending it. - Dev-server response shape deviations are accommodated, matching the workarounds in the Python POC and PHP PR:
  • GetStreamProcessor unwraps a top-level result wrapper when the server returns { ok: 1, result: { … } }.
  • GetMoreSampleStreamProcessor accepts both nextBatch (spec) and messages (current dev server). - StreamProcessorInfo::id and pipeline_version are Option<T> rather than required.
• samples() is a single-command dispatch: absent / zero cursor_id → startSampleStreamProcessor (returns cursor_id, empty docs); non-zero cursor_id → getMoreSampleStreamProcessor. Callers stop when cursor_id ==0.
• State strings are returned as plain String, not an enum — per the spec, drivers MUST surface unknown state values as-is rather than mapping to a closed set.
• Internal-only fields (tenantID, projectId, processorId) are not surfaced in the user-facing API.

Test plan

• cargo check -p mongodb clean
• cargo clippy -p mongodb --all-targets -- -D warnings — no new warnings on the new code (only pre-existing CSFLE-feature-gated dead-code warnings in client.rs / tracking_arc.rs that are present on main)
• cargo +nightly fmt --check -- --unstable-features clean
• cargo test -p mongodb --lib stream_processing::tests — 10 unit tests pass (URI detection for prod / staging / creds-and-port / case-insensitivity / four reject cases; async rejection paths for non-workspace URI and SRVscheme)
• Functional smoke test stream_processing::lifecycle in driver/src/test/stream_processing.rs runs the full create → start → stats → sample → stop → drop lifecycle. Self-skips via log_uncaptured unless MONGODB_STREAM_PROCESSING_URI is set to a real workspace endpoint — needs an Evergreen variant configured with workspace creds before it actually exercises in CI.