Implement EventHubs token refresh

[LarryOsterman]

Implement Event Hubs authorization token refresh.

Because AMQP is a connection-oriented protocol (unlike HTTP which is nominally a connectionless protocol), authorization tokens used by AMQP can expire while the connections are still active. To implement this, each EventHubs (and ServiceBus) client spawns a background task to refresh authorization tokens.

There are several elements to this PR:

1. Updated the AMQP library to use the async_trait trait rather than implementing async traits manually. This uncovered several subtle bugs in the AMQP implementation (mostly the Send trait being missing on certain types).
2. Added a new "task spawner" type to azure core to facilitate creating an asynchronous task from the current runtime (currently supported runtimes are "tokio" and "standard".
3. Updated the EventHubs ConnectionManager type to add a token refresh task which is launched when a path is first authorized.
   1. As a part of the ConnectionManager refactoring, the credential field was moved from the service client objects into the connection manager and the credential field was removed from the authorize_path method.
4. A clippy nightly suggested fix to the StdExecutor type to simplify the error case.

Note that the ConnectionManager has a number of #[cfg(test)] test hooks to enable unit testing the connection manager token refresh logic. That allows for in-isolation testing of the token refresh logic while not significantly impeding the functionality.

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

azure_core_amqp
azure_core
azure_messaging_eventhubs

[Copilot]

Pull Request Overview

This PR implements Event Hubs token refresh support and updates the AMQP library to use async_trait for cleaner, asynchronous trait implementations. Key changes include:

• Refactoring AMQP sender, receiver, connection, and management APIs to use async_trait along with adding +Send bounds on parameters.
• Introducing an asynchronous task spawner in azure_core, with implementations for tokio, standard, and wasm targets.
• Minor dependency and error mapping updates in Cargo.toml and process modules.

Reviewed Changes

Copilot reviewed 27 out of 27 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
sdk/core/azure_core_amqp/src/sender.rs	Updated async API definitions and added +Send bounds on parameters.
sdk/core/azure_core_amqp/src/receiver.rs	Converted API functions to async functions with appropriate +Send bounds.
sdk/core/azure_core_amqp/src/noop.rs	Updated noop implementations with async_trait.
sdk/core/azure_core_amqp/src/management.rs	Refactored management API to use async_trait and simplified method definitions.
sdk/core/azure_core_amqp/src/fe2o3/*.rs	Applied async_trait refactoring and added Send bounds across session, sender, receiver, etc.
sdk/core/azure_core_amqp/src/connection.rs	Transformed connection APIs to async functions with awaited inner calls.
sdk/core/azure_core_amqp/src/cbs.rs	Updated cbs APIs to use async_trait.
sdk/core/azure_core_amqp/Cargo.toml	Added async-trait as a workspace dependency.
sdk/core/azure_core/src/task/*	Introduced new task spawner implementations and comprehensive tests for asynchronous tasks.
sdk/core/azure_core/src/process/standard.rs	Simplified error mapping using io::Error::other.
sdk/core/azure_core/src/lib.rs	Exposed the new task module.

[heaths]

Just a couple nits/tips. I'd like to see a "flattening" of the standard_spawn.rs but I wouldn't hold up this PR for it. It made it a bit hard to follow because all of a sudden is felt like reading...gasp...VB and keeping prefaced whitespace in mind because important. 😉