[MSBUILD SDK] Add general msbuild props, use worker SDK

[jviau]

Issue describing the changes in this PR

part of #3131

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

Additional information

Adds some basic props to the new msbuild sdk. One major deviation this SDK is taking, is we will be using Microsoft.NET.Sdk.Worker SDK internally. This adds a few features on top of the regular .NET SDK

• Default copying of .content and .json files to build & publish output
• Default properties: OutputType=exe, DebugSymbols=true, DebugType=pdbonly, GenerateDependencyFile=true, IsPackable=false
• Default usings for some Microsoft.Extensions namespaces (Config, DI, Hosting, Logging)
• Project capabilities to give some nicer UX in Visual Studio (dynamic file nesting).

[Copilot]

Pull Request Overview

This PR introduces a new MSBuild SDK (Azure.Functions.Sdk) that will eventually replace the existing Microsoft.Azure.Functions.Worker.Sdk. The new SDK leverages Microsoft.NET.Sdk.Worker as its base to provide enhanced features like automatic content file copying, default project configurations, and improved Visual Studio integration.

Key Changes:

• Creates the new Azure.Functions.Sdk project with MSBuild props/targets files that import and build upon Microsoft.NET.Sdk.Worker
• Adds default package reference to Microsoft.Azure.Functions.Worker v2.0.0 and configures Azure Functions tooling integration
• Updates CI pipeline to include feature branches in code mirroring

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Azure.Functions.Sdk/Azure.Functions.Sdk.csproj	Defines the SDK project structure and packaging configuration
src/Azure.Functions.Sdk/Sdk/Sdk.props	Entry point props file that sets SDK flag and imports target-specific props
src/Azure.Functions.Sdk/Sdk/Sdk.targets	Entry point targets file that defines task paths and imports target-specific targets
src/Azure.Functions.Sdk/Targets/Azure.Functions.Sdk.props	Core props file that imports Worker SDK, sets defaults, and adds package references
src/Azure.Functions.Sdk/Targets/Azure.Functions.Sdk.targets	Core targets file that imports Worker SDK targets and configures Functions tooling
src/Azure.Functions.Sdk/Build/Azure.Functions.Sdk.targets	Guard targets to prevent incorrect PackageReference usage
src/Azure.Functions.Sdk/README.md	Documents the purpose of the new SDK
eng/ci/code-mirror.yml	Enables code mirroring for feature branches
DotNetWorker.sln	Adds the new SDK project to the solution

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