Upgrade Application Insights connection in Designer

[RonnyB71]

Description

Currently when you build Studio Designer backend you get a warning:

Severity	Code	Description	Project	File	Line	Suppression State
Warning	CS0618	'ApplicationInsightsExtensions.AddApplicationInsightsTelemetry(IServiceCollection, string)' is obsolete: 'InstrumentationKey based global ingestion is being deprecated. Use the AddApplicationInsightsTelemetry() overload which accepts Action<ApplicationInsightsServiceOptions> and set ApplicationInsightsServiceOptions.ConnectionString. See https://github.com/microsoft/ApplicationInsights-dotnet/issues/2560 for more details.'	Designer	C:\dev\altinn-studio\src\studio\src\designer\backend\Program.cs	193	Active

Today we use a instrumentation key to connect to Application Insights, moving forward we should use a ConnectionString instead as specified here https://docs.microsoft.com/en-us/azure/azure-monitor/app/migrate-from-instrumentation-keys-to-connection-strings

Additional Information

No response

Tasks

No response

Acceptance Criterias

• [ ] ConnectionString is used
• [ ] Warning is gone

[framitdavid]

Should add connectionString using TeraForm scripts.