chore(deps): update applicationinsights-dotnet monorepo to v3 (major)

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	OpenSSF
Microsoft.ApplicationInsights (source)	nuget	major	2.23.0 → 3.1.0
Microsoft.ApplicationInsights.AspNetCore (source)	nuget	major	2.23.0 → 3.1.0
Microsoft.ApplicationInsights.WorkerService (source)	nuget	major	2.23.0 → 3.1.0

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Release Notes

Microsoft/ApplicationInsights-dotnet (Microsoft.ApplicationInsights)

v3.1.0

• Make TelemetryContext properties public and propagate them via TelemetryClient.
• Add fallback to APPLICATIONINSIGHTS_CONNECTION_STRING environment variable for Base, Web, and NLog packages when connection string is not set via code.
• Update Azure.Monitor.OpenTelemetry.Exporter to 1.7.0. This includes updated mappings for telemetry context.
• Fix OTEL_SDK_DISABLED not being honored when TelemetryConfiguration.DisableTelemetry is set in DI scenarios., #​3157
• Fix TrackAvailability ignoring user-specified Timestamp on AvailabilityTelemetry. The timestamp is now emitted as microsoft.availability.testTimestamp so downstream exporters can use the correct event time.
• Added netstandard2.0 target framework to Microsoft.ApplicationInsights package to support customers with shared libraries targeting netstandard2.0.
• Fix TelemetryClient.Context.Cloud.RoleName set after construction now applies to all telemetry.
• Fix bug where Debug/Trace level logs from TrackTrace API were not emitted to Application Insights
• Fix Track API calls to not mutate the passed in dictionary if it is readonly
• Fix NullReferenceException in TelemetryClient.Flush() and FlushAsync() when called from DI scenarios
• Fix ApplicationVersion ignored: ApplicationInsightsServiceOptions.ApplicationVersion is now applied as service.version on the OpenTelemetry Resource for both AspNetCore and WorkerService packages
• Fix HttpRequestExtensions.UnvalidatedGetHeader always returning empty string instead of the actual header value. Restored max-length enforcement to guard against oversized header values.

v3.0.0

• Replaced netstandard2.0 with net8.0 target framework in Microsoft.ApplicationInsights.NLogTarget package.

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[AndreaCuneo]

@copilot investigate the ci build error linked to the v3 upgrade of application insights. get release not, websearch for upgrade instructions, check the source github repo.

[Copilot]

@AndreaCuneo I've opened a new pull request, #633, to work on those changes. Once the pull request is ready, I'll request review from you.