[cDAC] Implement ISOSDacImpl.GetAssemblyList

[max-charlamb]

As part of work for #114336, the cDAC now supports iterating Assemblies in an AppDomain so this API falls out nicely.

It is also used as part of !dumpdomain and is relatively easy to test.

[Copilot]

Pull Request Overview

This PR implements the ISOSDacImpl.GetAssemblyList API to support iterating assemblies within an AppDomain. Key changes include:

• Implementation of the GetAssemblyList method in SOSDacImpl.cs with appropriate argument checks, exception handling, and debug validation.
• Addition of new data types (e.g. LoaderAllocator, ArrayListBase, and related cdac_data specializations) and updates to the assembly and appdomain data models to support the new functionality.
• Updates to the ILoader interface and associated loaders in the DataContractReader.Contracts to enumerate assemblies based on various iteration flags.

Reviewed Changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/native/managed/cdacreader/src/Legacy/SOSDacImpl.cs	Implements the GetAssemblyList API with error checks and debug validation against legacy implementations.
src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Data/LoaderAllocator.cs	Introduces LoaderAllocator data type for tracking loader allocations.
src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Data/Assembly.cs	Extends the Assembly data type with new fields (Module, Error, NotifyFlags, Level) to support assembly status.
src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Data/ArrayListBase.cs	Provides implementation for ArrayListBase and its block elements using modern collection initialization.
src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Data/AppDomain.cs	Adds DomainAssemblyList field for improved assembly enumeration in AppDomains.
src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs	Updates ILoader contract with GetAssemblies and IsAssemblyLoaded methods.
Other coreclr and datadescriptor files	Updates to cdac_data and constant definitions to support the new APIs.

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[max-charlamb]

I'm not sure if there is a better way to access this global in the datadescriptors. Ideally, I don't want to change its access modifier.