Migrate Azure SDK to modern packages

[wendellmva]

Summary

Migrate from legacy Azure SDK packages to modern Azure.* packages.

Current Packages (to remove)

• Microsoft.Azure.Cosmos.Table 1.0.0
• Microsoft.Azure.Search 5.0.1
• Microsoft.Azure.Storage.Blob 9.4.1

New Packages (to add)

• Azure.Data.Tables 12.8.3
• Azure.Search.Documents 11.6.0
• Azure.Storage.Blobs 12.21.0
• Azure.Identity 1.12.0

Tasks

• Update src/BaGet.Azure/BaGet.Azure.csproj package references
• Refactor TablePackageDatabase.cs - CloudTable → TableClient
• Refactor AzureSearchService.cs - SearchServiceClient → SearchClient
• Refactor BlobStorageService.cs - CloudBlobClient → BlobServiceClient
• Update Azure configuration options
• Add Azure.Identity for modern auth

Breaking Changes

The entire Azure SDK has been redesigned. All service classes need refactoring.

Dependencies

• Depends on .NET 9 upgrade