Add central project configuration and update package references

[ptr727]

• Introduced Directory.Build.props and Directory.Packages.props for shared MSBuild properties and centralized NuGet package versions.
• Updated various project files to remove specific properties and use centralized versions.
• Enhanced GitHub workflows for code generation and pull requests.
• Refactored launch configurations and tasks for better organization.

Signed-off-by: Pieter Viljoen ptr727@users.noreply.github.com

[Copilot]

Pull request overview

This PR centralizes shared build configuration and NuGet package versioning across the solution, and updates editor/CI configuration to align with the new centralized setup.

Changes:

• Added Directory.Build.props for shared MSBuild properties (TFM, analyzers, warnings-as-errors, artifacts path, etc.).
• Added Directory.Packages.props to centrally manage NuGet package versions and removed per-project Version attributes.
• Updated VS Code config and GitHub workflows to reflect the new artifacts/output and codegen concurrency behavior.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
Tests/Tests.csproj	Removes per-project build settings and inlines; relies on centralized properties and CPM package versions.
Tests/GlobalUsings.cs	Removes now-redundant System global usings (covered by implicit usings).
Library/LogOptions.cs	Removes redundant System.Threading using (covered by implicit usings).
Library/Library.csproj	Removes duplicated analyzer/nullable/TFM settings and switches to CPM package references.
Library/GlobalUsings.cs	Removes redundant System global using.
Directory.Packages.props	Introduces centralized package versions for the solution.
Directory.Build.props	Introduces centralized MSBuild properties shared by all projects.
Console/GlobalUsings.cs	Removes redundant System* global usings (covered by implicit usings).
Console/Console.csproj	Removes duplicated properties and switches to CPM package references.
CodeGen/GlobalUsings.cs	Removes redundant System* global usings (covered by implicit usings).
CodeGen/CodeGen.csproj	Removes duplicated properties and switches to CPM package references; normalizes project file header.
CodeGen/CodeGen.cs	Updates the generated timestamp constant.
Benchmarks/GlobalUsings.cs	Removes redundant System global using.
Benchmarks/Benchmarks.csproj	Removes duplicated properties and switches to CPM package reference.
AGENTS.md	Documents the new centralized build/package configuration approach.
.vscode/tasks.json	Adds a benchmark task aligned with the .artifacts layout.
.vscode/launch.json	Updates debug launch paths to the .artifacts output layout.
.github/workflows/run-periodic-codegen-pull-request.yml	Adjusts concurrency grouping to target main/codegen consistently.
.github/workflows/run-periodic-codegen-app-pull-request.yml	Adjusts concurrency grouping to target main/codegen consistently.
.github/copilot-instructions.md	Documents the new centralized MSBuild and CPM setup.