fix(iot-dev): avoid MQTT cast during reconnect

[Arnab Nandy (arnabnandy7)]

Checklist

• I have read the [contribution guidelines] (https://github.com/Azure/azure-iot-sdk-java/blob/main/.github/CONTRIBUTING.md).
• I added or modified the existing tests to cover the change (we do not allow our test coverage to go down).
• I submitted this PR against the correct branch:
  • This pull-request is submitted against the main branch.

Reference/Link to the issue solved with this PR (if any)

Fixes #1853

Description of the problem

Non-multiplexed clients maintain a device connection state entry for status tracking. The reconnect logic checked this state regardless of whether the transport was multiplexing.

During a close/reconnect race, an MQTT client's transport-level status could be DISCONNECTED while its device state remained DISCONNECTED_RETRYING. This caused the reconnect flow to treat the MQTT connection as a multiplexed AMQP connection and cast MqttIotHubConnection to AmqpsIotHubConnection, resulting in a ClassCastException.

Description of the solution

Updated IotHubTransport.needsReconnect() so that device-session reconnect states are checked only when the transport is multiplexing. Transport-level reconnection behavior remains unchanged for non-multiplexed clients, while AMQP multiplexing continues to reconnect individual device sessions as before.

Added regression tests verifying that:

• Non-multiplexed transports ignore device-session reconnect state.
• Multiplexed transports continue to honor device-session reconnect state.

Targeted test results:

Tests run: 74, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS