Rename getPeerID()

[btoms20]

What:

• Rename the following function

Multiaddr.getPeerID() -> String

Why:

• The current implementation doesn't return a PeerID but a string rep of the ID instead
• Due to PeerID (swift-peer-id) not being a dependency of Multiaddr (swift-multiaddr) we can't return an actual PeerID

Proposed Change:

• Rename to

Multiaddr.getPeerIDString() -> String

• Then in swift-libp2p-core, we can extend Multiaddr with a proper method

// either
Multiaddr.getPeerID() -> PeerID?
// or
Multiaddr.getPeerID() throws -> PeerID