Add .NET Feature Management 4.6.0 release notes

[Copilot]

Prepares customer-facing release notes for .NET Feature Management 4.6.0 based on the keyed dependency injection support added in the related FeatureManagement-Dotnet PR.

• Microsoft.FeatureManagement

  • Added the 4.6.0 enhancement entry for resolving variant service implementations through keyed dependency injection.
  • Calls out lazy, on-demand instantiation for variant implementations with their own dependencies and configuration.

• Related packages

  • Added matching 4.6.0 reference-update entries for:
    • Microsoft.FeatureManagement.AspNetCore
    • Microsoft.FeatureManagement.Telemetry.ApplicationInsights

[Copilot]

Pull request overview

Adds customer-facing release notes for the .NET Feature Management 4.6.0 release across the core package and two related packages, documenting the keyed dependency injection variant-resolution enhancement and updating dependent package reference entries.

Changes:

• Added a 4.6.0 release notes entry to Microsoft.FeatureManagement describing keyed DI-based variant implementation resolution (with lazy/on-demand instantiation note and issue link).
• Added 4.6.0 reference-update entries for Microsoft.FeatureManagement.AspNetCore and Microsoft.FeatureManagement.Telemetry.ApplicationInsights pointing to the core release notes.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
releaseNotes/Microsoft.Featuremanagement.md	Adds the 4.6.0 enhancement entry describing keyed DI variant resolution.
releaseNotes/Microsoft.Featuremanagement.AspNetCore.md	Adds a 4.6.0 entry updating the Microsoft.FeatureManagement reference and linking to core notes.
releaseNotes/Microsoft.Featuremanagement.Telemetry.ApplicationInsights.md	Adds a 4.6.0 entry updating the Microsoft.FeatureManagement reference and linking to core notes.