.NET: [BREAKING] Update type names and source generator to reduce conflicts

[lokitoth]

Motivation and Context

Some of the names of types used by workflows are likely to be conflicting (or are conflicting) with other types from, e.g. ASPNetCore.WebAPI. (#4174).

Description

• Rename Config to ExecutorConfig, as it is only used when binding to an Executor factory function.
• Make Configured and relevant extension method classes internal (this is implementation details)
• Fix the Source Generator to explicitly import RouteBuilder: fixes .NET: [Bug]: [Workflow Generator] 'RouteBuilder' is an ambiguous reference between 'Microsoft.AspNetCore.Routing.RouteBuilder' and 'Microsoft.Agents.AI.Workflows.RouteBuilder' #4174
• Closes .NET: Some Microsoft.Agents.Workflows type names are much too general #963

Explicitly not changing Edge, or Run for now unless we see actual conflicts.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR addresses type-name conflicts in the .NET Workflows surface area (notably RouteBuilder ambiguity with ASP.NET Core) by renaming configuration types, tightening visibility of implementation details, and adjusting generated source to avoid ambiguous references.

Changes:

• Renames Config/Config<TOptions> to ExecutorConfig/ExecutorConfig<TOptions> and updates relevant binding APIs.
• Makes Configured and related configuration extension classes internal to reduce public API surface and naming collisions.
• Updates the workflow source generator output to add a RouteBuilder using-alias to disambiguate against ASP.NET Core.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
dotnet/src/Microsoft.Agents.AI.Workflows/ExecutorConfig.cs	Renames Config types to ExecutorConfig variants.
dotnet/src/Microsoft.Agents.AI.Workflows/ExecutorBindingExtensions.cs	Updates executor binding extension signatures to use ExecutorConfig<TOptions>.
dotnet/src/Microsoft.Agents.AI.Workflows/Configured.cs	Makes Configured* types internal and updates factories to use ExecutorConfig.
dotnet/src/Microsoft.Agents.AI.Workflows/ConfigurationExtensions.cs	Makes configuration extension class internal (implementation detail).
dotnet/src/Microsoft.Agents.AI.Workflows.Generators/Generation/SourceBuilder.cs	Adds RouteBuilder alias in generated code to prevent ambiguous reference errors.

Comments suppressed due to low confidence (1)

dotnet/src/Microsoft.Agents.AI.Workflows/ExecutorConfig.cs:10

• ExecutorConfig was renamed to reduce naming conflicts and is described in the PR as being used for executor factory binding, but the XML summary still describes a generic "configuration for an object". Consider updating the XML docs to describe the executor-factory scenario (and the intended semantics of the required id parameter) so the public API docs match the new type name.