add asp commands

[nickpoindexter]

Summary

Adds first-class driver support for Atlas Stream Processing (ASP), implementing the ASP driver spec. Users currently have to drop down to
client.GetDatabase("admin").RunCommand(...) against a workspace endpoint; this PR adds a dedicated client / handles layer matching what's already shipped for PHP, Rust, and Ruby.

What's new

Public API (src/MongoDB.Driver/StreamProcessing/)

• StreamProcessingClient — workspace-scoped client distinct from MongoClient. Validates the workspace URI (atlas-stream-*.<region>.a.query.mongodb.net and the .mongodb-<env>.net staging variants), enforces TLS, defaults authSource to
  admin. Implements IDisposable and disposes the underlying MongoClient. Static StreamProcessingClient.IsWorkspaceUri(uri) exposed for callers that want to gate before connecting.
• StreamProcessors — Create / Get / GetInfo (plus Async pairs) for managing processors in a workspace.
• StreamProcessor — Start / Stop / Drop / Stats / Samples (plus Async pairs) for a named processor.
• StreamProcessorInfo — typed accessor over the getStreamProcessor response. Fields the spec marks as optional (e.g. Id, PipelineVersion) are Nullable<T> / nullable reference types.
• StreamProcessorSamples — result of Samples / SamplesAsync, exposes CursorId, Documents, IsExhausted.
• Options: CreateStreamProcessorOptions, StartStreamProcessorOptions, FailoverOptions, GetStreamProcessorStatsOptions, GetStreamProcessorSamplesOptions. POCO classes following the existing options-class convention.

Wire commands
All 8 ASP commands routed through IMongoDatabase.RunCommand / RunCommandAsync against the admin database: createStreamProcessor, startStreamProcessor, stopStreamProcessor, dropStreamProcessor, getStreamProcessor,
getStreamProcessorStats, startSampleStreamProcessor, getMoreSampleStreamProcessor.

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 PHP / Rust / Ruby PRs:
  • StreamProcessors.GetInfo unwraps a top-level result wrapper when the server returns { ok: 1, result: { … } }.
  • StreamProcessor.Samples accepts both nextBatch (spec) and messages (current dev server).
  • StreamProcessorInfo.Id and PipelineVersion return null when the server omits them.
• Samples is a single-call dispatch: null/zero CursorId → startSampleStreamProcessor (returns StreamProcessorSamples with cursor id, empty docs); non-zero → getMoreSampleStreamProcessor. Callers stop when CursorId == 0 (or use
  the IsExhausted predicate).
• State strings returned as plain strings, not enums — 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 public API.

Test plan

• dotnet build CSharpDriver.sln — 0 errors (14 pre-existing warnings: SharpCompress vulnerability + netcoreapp3.1 TFM support notices, neither introduced by this PR)
• dotnet test tests/MongoDB.Driver.Tests/MongoDB.Driver.Tests.csproj -f net10.0 --filter "FullyQualifiedName~StreamProcessing" — all unit tests pass (URI detection for prod / staging / creds-and-port / case-insensitivity / four reject
  cases; constructor rejection paths; full StreamProcessorInfo getter coverage including defaults and error fields; StreamProcessorSamples predicates)
• dotnet test ... --filter "FullyQualifiedName~StreamProcessingLifecycle" (no env var) — self-skips cleanly
• Full lifecycle exercised against an Atlas staging workspace via tests/MongoDB.Driver.Examples/StreamProcessingExample.cs — create → start → stats → samples (cursor opened + telemetry docs returned in second call) → stop → drop. All
  transitions clean.