[AMQP] Receiver cannot send Modified or annotated Rejected dispositions

## Summary

`AmqpReceiverApis` in `sdk/core/azure_core_amqp/src/receiver.rs` exposes only `accept_delivery`, `reject_delivery`, and `release_delivery`. There is no way to settle a delivery with an AMQP `Modified` outcome, and `reject_delivery` accepts no error condition or description.

## Motivation

Service Bus needs four settlement dispositions and three distinct AMQP outcomes. Abandon is `Modified` with `undeliverable-here` set to false. Defer is `Modified` with `undeliverable-here` set to true. Dead letter is `Rejected` with a reason and a description. None of the three can be expressed today.

The effect on `azure_messaging_servicebus` is silent data loss. `Receiver::abandon_message` calls `release_delivery` and drops `properties_to_modify`. `Receiver::dead_letter_message` calls `reject_delivery` and drops `reason`, `error_description`, and `properties_to_modify`. The caller receives `Ok(())` in both cases.

`AmqpOutcome::Modified` already exists in `sdk/core/azure_core_amqp/src/messaging.rs`, but it describes a send outcome. No receiver side API applies it.

## Proposal

Extend `AmqpReceiverApis` so a delivery can be settled with the full AMQP outcome set.

- Add a `Modified` disposition that carries `delivery-failed`, `undeliverable-here`, and `message-annotations`.
- Give the `Rejected` disposition an error condition and an optional description.
- Keep the existing three methods, or replace them with one disposition method that takes an outcome. Pick whichever fits the crate's stability guarantees.

Sub-issue of #4934.

Start with sdk/core/azure_core_amqp/src/receiver.rs and compare its settlement methods with AmqpOutcome::Modified in sdk/core/azure_core_amqp/src/messaging.rs. Trace abandon_message and dead_letter_message in azure_messaging_servicebus to understand the dropped fields. Done means receiver settlement can express Modified and Rejected outcomes with the specified fields and callers no longer silently discard them.

Written by the indexing model from the issue text.