PluggableUSB iSerialNum buffer overflow

`PluggableUSB_::getShortName` and `PluggableUSBModule::getShortName` should not only get a char pointer as argument, but also the size of the buffer. I have currently the problem that i don't know how many chars I can copy to the pointer, without producing a overflow. So if other `PluggableUSBModule`'s appended some characters, I have less space for my string. But currently I can't know that, because the remaining size of the buffer is not given.

Start by locating PluggableUSB_::getShortName and PluggableUSBModule::getShortName and trace how their character buffers are assembled. Check the callers and any existing USB descriptor-related tests or examples. Done means the available buffer size is known at each call and appended strings cannot overflow it.

Written by the indexing model from the issue text.