.NET Declarative Workflows - Update workflow scope semantics

[crickman]

Copilot Studio specifies workflow scoped variables as Topic scope.

For Foundry Workflows, we want to use Workflow scope to mean the same thing.

This involves:

1. Adding support to Copilot Studio Object Model (& Runtime)
2. Updating agent-framework dependency on the Copilot Studio Object Model
3. Change usage of VariableScopeNames.Topic to VariableScopeNames.Workflow

Sample workflows required update at (https://github.com/microsoft/agent-framework/tree/main/workflows).

[crickman]

In progress for the upcoming week (integration on 9/29)

[crickman]

Resolved in #944

Instead of "Workflow" its "Local"