[BUG] RECEIVE_MAXIMUM, TOPIC_ALIAS should be unsignedShort

[DongyuanPan]

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• Bug exists Release Version 1.2.5 ( Master Branch)
• Bug exists in MQTTv3 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)
• Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

According to the MQTT 5.0 protocol, RECEIVE_MAXIMUM should be in the range [0, 65535], but when the property is resolved, readShort() is used, which causes the range to be [-32768, 32767].
For example, if the server sends 65535(0xFFFF), the parsing will overflow and RECEIVE_MAXIMUM will be -1.

TOPIC_ALIAS_MAXIMUM and TOPIC_ALIAS the same as RECEIVE_MAXIMUM.