Adopt generated client stubs (source generation) across samples

[romanett]

Sub-issue of #755.

Why

Part of #755 is moving client samples onto generated client stubs — i.e. the C# source generator that implements IEncodeable (Encode/Decode/IsEqual/Clone) and type activators for custom OPC UA data types, instead of hand-written or ModelCompiler-emitted stub classes. The OPCFoundation.NetStandard.Opc.Ua.SourceGeneration analyzer package is already referenced by some projects in this repo.

Scope

Client-side custom data type / model stub code across the samples, e.g.:

• Workshop/DataTypes (custom data types)
• Workshop/Boiler, Workshop/SimpleEvents, Workshop/AlarmCondition model/type classes
• Any other sample with hand-written or generated IEncodeable stub classes consumed by clients (audit repo-wide)

Tasks

1. Add the OPCFoundation.NetStandard.Opc.Ua.SourceGeneration package as an analyzer (OutputItemType="Analyzer" ReferenceOutputAssembly="false") to the affected projects.
2. Convert custom data types to partial classes/enums annotated with [DataType(Namespace = "...")]; remove hand-written Encode/Decode/IsEqual/Clone and manual activator registration — let the generator emit them.
3. Verify complex-type reads/writes still round-trip on the client (works with Opc.Ua.Client.ComplexTypes).
4. Confirm the generated TypeId/BinaryEncodingId/XmlEncodingId match the sample server nodesets.

Note: please confirm with maintainers whether "generated client stubs" in #755 also covers a specific typed service/method-stub generator beyond source-generated data types; adjust scope if so.

References

• https://github.com/OPCFoundation/UA-.NETStandard/blob/master/docs/SourceGeneratedDataTypes.md
• https://github.com/OPCFoundation/UA-.NETStandard/blob/master/docs/ComplexTypes.md

Acceptance criteria

• Affected sample projects build with the source generator; no hand-written IEncodeable boilerplate remains for the converted types.
• Clients still encode/decode and display custom data types correctly against the sample servers.

Dependencies

Can proceed in parallel with the session/subscription sub-issues; coordinate merge order to avoid churn in the same client files.