Fix project dependencies

[cheenamalhotra]

Also fixes building solution in VS Code.

[Copilot]

Pull Request Overview

This PR fixes project dependencies by adding missing Azure.Core package references and consolidating dependency management. The changes ensure that Azure.Core is properly referenced across all target frameworks and project types, while also standardizing how certain dependencies are managed.

• Adds Azure.Core dependency to all target frameworks in the NuGet package specification
• Consolidates package references by moving common dependencies to the main project file
• Adds Azure.Core package reference to all .NET Framework and .NET Core project files

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/specs/Microsoft.Data.SqlClient.nuspec	Adds Azure.Core dependency to all target framework groups
src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj	Consolidates package references and adds missing dependencies
src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj	Adds Azure.Core package reference for .NET Framework implementation
src/Microsoft.Data.SqlClient/netfx/ref/Microsoft.Data.SqlClient.csproj	Adds Azure.Core package reference for .NET Framework reference assembly
src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj	Adds Azure.Core package reference for .NET Core implementation
src/Microsoft.Data.SqlClient/netcore/ref/Microsoft.Data.SqlClient.csproj	Adds Azure.Core package reference for .NET Core reference assembly

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