Phase 2 follow-up: Implement full MediaStreamTrack constraint solver parity

[General-Fault]

Current plan for #50 is staged delivery: native plumbing + marshalling + explicit failure paths, with full constraint solving deferred.

This follow-up tracks implementing full MediaStreamTrack.applyConstraints() parity behavior.

Problem

ApplyConstraints currently does not implement full constraint selection/fitness-distance solving behavior. Staged #50 intentionally defers full solver semantics.

Goal

Implement full constraints algorithm behavior aligned with W3C Media Capture and Streams and Google Blink/libwebrtc expectations, including:

• Required vs ideal handling across MediaTrackConstraintSet and advanced
• Candidate selection / fitness-distance style evaluation
• Overconstrained-style failure semantics for unsatisfiable required constraints
• Observable behavior parity for ordering and error surfaces

Scope

• WebRtcInterop native/interop logic behind MediaStreamTrack::ApplyConstraints
• Interop and managed tests validating solver behavior
• Explicit documentation of any unavoidable .NET/runtime divergence

Acceptance criteria

• Required constraints that cannot be satisfied fail deterministically with explicit error
• Ideal constraints influence selection when multiple candidates satisfy required constraints
• advanced sets are evaluated in order per spec processing model
• Tests cover success paths, unsatisfiable required constraints, and ordering-sensitive cases

References

• W3C constraints model: https://www.w3.org/TR/mediacapture-streams/#constraints
• applyConstraints: https://www.w3.org/TR/mediacapture-streams/#dom-mediastreamtrack-applyconstraints
• Repo crosswalk notes: docs/standards/crosswalk/webrtcnet-api-to-spec.md