Replace deprecated Microsoft.Azure.ApplicationInsights.Query with Azure.Monitor.Query

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This PR migrates the codebase from the deprecated Microsoft.Azure.ApplicationInsights.Query package to the new Azure.Monitor.Query package, as required by Microsoft's deprecation announcement.

Background

Microsoft deprecated Microsoft.Azure.ApplicationInsights.Query in favor of Azure.Monitor.Query, with support ending on March 31, 2023. The migration guide is available at https://aka.ms/azsdk/net/migrate/ai-monitor-query.

Changes Made

Package Reference Update

• Updated from Microsoft.Azure.ApplicationInsights.Query v1.0.0 to Azure.Monitor.Query v1.5.0 in LogInsights.csproj

API Migration in AppInsightsLogReader.cs

• Authentication: Implemented custom AppInsightsApiKeyCredential class extending TokenCredential for API key authentication
• Client: Replaced ApplicationInsightsDataClient with LogsQueryClient
• Query Execution: Updated from events.Client.Query.ExecuteAsync() to _client.QueryWorkspaceAsync()
• Data Processing: Enhanced type safety with proper null checking and type conversion for the new result format
• Time Range Handling: Updated to use QueryTimeRange objects instead of string-based timespan parameters

Key Technical Details

The new Azure.Monitor.Query package is designed for Azure Monitor Logs (Log Analytics workspaces), which is what Application Insights uses under the hood. The migration maintains backward compatibility while using the modern, supported SDK.

// Old approach
var client = new ApplicationInsightsDataClient(new ApiKeyClientCredentials(apiKey));
var result = await events.Client.Query.ExecuteAsync(appId, query, timespan);

// New approach  
var credential = new AppInsightsApiKeyCredential(apiKey);
var client = new LogsQueryClient(credential);
var result = await client.QueryWorkspaceAsync(appId, query, timeRange);

The migration ensures the Application Insights log reading functionality continues to work with the supported Azure SDK while removing dependency on the deprecated package.

Fixes #111.

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