Packing Legacy cDAC apis

[rcj1]

This PR does some work and refactoring in order to facilitate a private version of the cDAC.

1. Assuming that we may want to access some of the legacy APIs from the private cDAC, I have pulled the legacy code into a separate package and made the COM interop classes public for use.
2. I have added a mechanism to add new contract implementations to a target upon instantiation of the target. This way the private cDAC can add its own contracts.
3. Exposing GetContract. The private cDAC can in the future call GetContract with contracts not found in the default contract registry. This will probably be hidden behind an extension method but we need GetContract public for implementation.

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[Copilot]

Pull Request Overview

This PR refactors the legacy cDAC APIs to support a future private cDAC implementation by:

• Extracting legacy code into a separate package (Microsoft.Diagnostics.DataContractReader.Legacy) with public visibility
• Adding extensibility for custom contract implementations via additionalFactories parameter
• Exposing GetContract<TContract>() publicly to enable access to contracts outside the default registry

Reviewed Changes

Copilot reviewed 23 out of 25 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
mscordaccore_universal.csproj	Updates project reference to point to the new Legacy package and removes obsolete Interop.BOOL.cs reference
Entrypoints.cs	Makes entrypoint methods public and passes null for additionalFactories parameter in initialization calls
ContractDescriptorTarget.cs	Adds additionalFactories parameter to creation methods and passes it to CachingContractRegistry
CachingContractRegistry.cs	Adds logic to register additional contract factories during initialization
TypeNameBuilder.cs	Changes visibility to public and fixes ArgumentException constructor call
SOSDacImpl.cs	Changes class visibility from internal to public
SOSDacImpl.IXCLRDataProcess.cs	Changes class visibility to public and seals EnumMethodInstances class
SOSDacImpl.ICLRDataEnumMemoryRegions.cs	Changes class visibility from internal to public
OutputBufferHelpers.cs	Changes class visibility from internal to public
Microsoft.Diagnostics.DataContractReader.Legacy.csproj	New project file for the Legacy package
Interop.BOOL.cs	New file containing BOOL enum previously shared via CommonPath
IXCLRData.cs	Changes all interface and struct visibility from internal to public
ISOSDacInterface.cs	Changes all interface, struct, and enum visibility from internal to public
ICLRData.cs	Changes interface visibility from internal to public
ConversionExtensions.cs	Changes class and ToAddress method visibility to public
ClrDataTask.cs	Changes class visibility from internal to public
ClrDataStackWalk.cs	Changes class visibility from internal to public
ClrDataModule.cs	Changes class visibility from internal to public
ClrDataMethodInstance.cs	Changes class visibility from internal to public
ClrDataFrame.cs	Changes class visibility from internal to public
ClrDataAddress.cs	Changes struct and marshaller visibility from internal to public
IContractFactory.cs	Adds ContractType property to interface
ContractRegistry.cs	Adds abstract GetContract() method