integration-app: Reduce binary code size with debug experience

Change the optimization level for the `freertos-iot-libraries-tests`
application to reduce code size whilst still maintaining a
comfortable debugging experience.

Arm Compiler For Embedded optimization level is set to use `-O1` and
Arm GNU Toolchain is set to use `-Og`.
These optimization levels are already used by the other FRI
applications.

The Arm Compiler For Embedded `-O1` optimization level results
in a slower binary execution speed on `FVP_Corstone_SSE-310`.
The MQTT test process loop timeout period
(`MQTT_TEST_PROCESS_LOOP_TIMEOUT_MS`) needs therefore to be
increased from `40000` to `54630` to pass the
`MqttTest, MQTT_Restore_Session_Duplicate_Incoming_Publish_Qos1`
test case.

Signed-off-by: Hugues Kamba Mpiana <hugues.kambampiana@arm.com>