* Moved the `MemoryChannel::copy()` method out of the `MemoryChannel` as
a standalone function.
* Renamed `mscclpp::putPackets()` and `mscclpp::getPackets()` to
`mscclpp::copyToPackets()` and `mscclpp::copyFromPackets()` respectively
for consistency.
* Renamed `MemoryChannel::getPackets()` to
`MemoryChannel::unpackPackets()` for clarity. Renamed `getPacketBuffer`
to `packetBuffer`.
* Added the `MemoryChannel::unpackPacket()` method that unpacks one
packet in the buffer.
* Added the `BaseMemoryChannel` class that only contains a semaphore
without memory addresses.
* Removed the `MemoryDevice2DeviceSemaphoreDeviceHandle::signalPacket()`
method that is lacking use cases.
