Further code quality improvements

...de/justjanne/coverageconverter/CoverageConverterPlugin.kt

libquassel-protocol/build.gradle.kts

...lin/de/justjanne/libquassel/protocol/io/ByteBufferUtil.kt

...janne/libquassel/protocol/models/BackendInfoSerializer.kt

.../justjanne/libquassel/protocol/models/HandshakeMessage.kt

...in/de/justjanne/libquassel/protocol/models/NetworkInfo.kt

...n/de/justjanne/libquassel/protocol/models/ids/SignedId.kt

...justjanne/libquassel/protocol/models/types/QuasselType.kt

...ssel/protocol/serializers/SignalProxyMessageSerializer.kt

...protocol/serializers/handshake/CoreSetupDataSerializer.kt

...l/protocol/serializers/handshake/SessionInitSerializer.kt

...ibquassel/protocol/serializers/qt/ByteBufferSerializer.kt

.../libquassel/protocol/serializers/qt/QVariantSerializer.kt

...ssel/protocol/serializers/quassel/BufferInfoSerializer.kt

...uassel/protocol/serializers/quassel/IdentitySerializer.kt

...ssel/protocol/serializers/quassel/IrcChannelSerializer.kt

...quassel/protocol/serializers/quassel/IrcUserSerializer.kt

...tocol/serializers/signalproxy/HeartBeatReplySerializer.kt

...l/protocol/serializers/signalproxy/HeartBeatSerializer.kt

...el/protocol/serializers/signalproxy/InitDataSerializer.kt