refactor: add Pubkey, Privkey, NoteId string aliases

This is a non-behavioral change in preparation for the actual switchover
from Strings to Ids. The purpose of this kit is to reduce the size of
the switchover commit which is going to be very large.

damus/Views/Muting/MutelistView.swift

@@ -9,9 +9,9 @@ import SwiftUI
 
 struct MutelistView: View {
     let damus_state: DamusState
-    @State var users: [String]
+    @State var users: [Pubkey]
     
-    func RemoveAction(pubkey: String) -> some View {
+    func RemoveAction(pubkey: Pubkey) -> some View {
         Button {
             guard let mutelist = damus_state.contacts.mutelist else {
                 return