Some improvements

[hax0r31337]

list of changes

• correct example, there no such method called setPacketCodec but setCodec in BedrockSession
• grant execute permission to gradlew
• use sha256 from natives library, this can make the progress faster on linux
• remove AES_FACTORY from EncryptionUtils, it's unused and will slow down the initialize progress
• change the supplier creating new instance for packets from Lmbda to java ::new, this change can make the library usable on Android