Access to workflow/activity instance created by Temporal from workflow/activity context where applicable

Describe the solution you'd like

For instances created by Temporal, they should be accessible from the context. Users want to access the actual class instance of a workflow from, say, an interceptor. This needs to be made available from the workflow context as the "instance". Note this is not applicable to Go and TypeScript. And for Java, PHP, Ruby, and .NET (DI only), the activity instance should be made available from the activity context (since they create the instance and control its lifetime).

• Go - N/A
• Java - https://github.com/temporalio/sdk-java/issues/2361
• Core - N/A
• TypeScript - N/A: Workflows and Activities are simple functions, not classes
• Python - https://github.com/temporalio/sdk-python/issues/720
• .NET - https://github.com/temporalio/sdk-dotnet/issues/388
• Ruby - https://github.com/temporalio/sdk-ruby/issues/180
• PHP - https://github.com/temporalio/sdk-php/issues/546
• Temporal CLI - N/A

Start by reviewing the linked issues for the Java, Python, .NET, Ruby, and PHP SDKs, since this feature spans multiple repositories and excludes Go and TypeScript. Done means applicable workflow or activity contexts expose the Temporal-created instance while preserving the stated language-specific exclusions and activity lifetime constraints.