Remove pkgproj projects that can be easily replaced by .NET SDK pack support

[jkoritzinsky]

Contributes to #75966

[Copilot]

Pull Request Overview

This pull request modernizes package creation by replacing legacy .pkgproj projects with .NET SDK's native pack support, directly implementing package metadata in the source projects themselves.

Key Changes:

• Converted ILVerify, ILVerification, and ILCompiler.Reflection.ReadyToRun to use SDK-style packaging
• Migrated Microsoft.NET.Sdk.IL from .pkgproj to .proj with SDK-style packaging
• Consolidated shared packaging logic into reusable pkgproj.props and pkgproj.targets files

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
ILCompiler.Reflection.ReadyToRun.csproj	Added IsPackable and package metadata properties
ILVerify.csproj	Added packaging properties for dotnet tool support
ILVerification.csproj	Added package metadata and release notes
pkgproj.targets	New shared packaging targets for symbol file handling
pkgproj.props	New shared packaging properties for .pkgproj projects
dotnet-ilverify.pkgproj	Deleted legacy packaging project
DotnetToolSettings.xml	Deleted obsolete tool settings file
coreclr-packages.proj	Updated to reference new SDK-style projects
Microsoft.NET.Sdk.IL.proj	New SDK-style packaging project
Microsoft.NET.Sdk.IL.pkgproj	Deleted legacy packaging project
Microsoft.NET.Sdk.IL/Directory.Build.targets	New targets file with packaging logic
Microsoft.NET.Sdk.IL/Directory.Build.props	New props file to control pkgproj usage
Microsoft.ILVerification.pkgproj	Deleted legacy packaging project
ILCompiler.Reflection.ReadyToRun.Experimental.pkgproj	Deleted legacy packaging project
.nuget/Directory.Build.targets	Simplified to import shared pkgproj.targets conditionally
.nuget/Directory.Build.props	Simplified to import shared pkgproj.props conditionally
Subsets.props	Added ILVerify and ILVerification to build list

[Copilot]

The package type should be 'MSBuildSdk' to match the original .pkgproj file, not 'DotNetSdk'.

Suggested change

	<PackageType>DotNetSdk</PackageType>
	<PackageType>MSBuildSdk</PackageType>

[Copilot]

The property should use $(PackageVersion) instead of $(Version) to match the original .pkgproj behavior, which used CalculatePackageVersion.

Suggested change

	Properties="IlAsmVersion=$(Version)">
	Properties="IlAsmVersion=$(PackageVersion)">

[dotnet-policy-service]

Tagging subscribers to this area: @hoyosjs
See info in area-owners.md if you want to be subscribed.