Copy packets to prevent AddressSanitizer: stack-use-after-return on address

[kirsteins]

Enabling the "Address Sanitizer" with the "Detect use of stack after return" feature has exposed a stack-use-after-return issue in the following code example:

import AudioKit
import CoreMIDI

private func createTestMIDIPacketList() -> MIDIPacketList {
    let midiData: [UInt8] = [0x90, 60, 90]
    let packetListPointer = UnsafeMutablePointer<MIDIPacketList>.allocate(capacity: 1)
    var packet = MIDIPacketListInit(packetListPointer)
    let timeStamp: MIDITimeStamp = 0
    packet = MIDIPacketListAdd(packetListPointer, 512, packet, timeStamp, midiData.count, midiData)
    return packetListPointer.pointee
}

func triggerAddressSanitizerWithUseOfStackAfterReturn() {
    for packet in createTestMIDIPacketList() {
        // Accesses packet via iterator and cause
        // AddressSanitizer: stack-use-after-return on address
    }
}

This pull request copies all MIDIPacket instead of iterating them one by one and fixes the issue with address sanitizer.

Please discuss if this is a good idea.

[kirsteins]

Tagging @wtholliday since you fixed the previous issue with address sanitizer in this file. Feedback welcomed and appreciated!

[aure]

I'll approve because MIDI is going to be very different in forthcoming versions of AudioKit anyway, so this seems fine to do for now, but I'll let @wtholliday chime in if he wants to, before merging later today.