Fix connections list index

This MR fixes the issue: [Connections screen] Connections list letters are not matching user's usernames.

What was done

• Refactor ContactListTableController
• Remove broken IndexedListCollator
• Collate contacts list using localized index

Sources/ContactListFeature/Helpers/IndexedListCollator.swift

-import UIKit
-import XXModels
-
-public protocol IndexableItem {
-    var indexedOn: NSString { get }
-}
-
-class IndexedListCollator<Item: IndexableItem> {
-    private final class CollationWrapper: NSObject {
-        let value: Any
-        @objc let indexedOn: NSString
-
-        init(value: Any, indexedOn: NSString) {
-            self.value = value
-            self.indexedOn = indexedOn
-        }
-
-        func unwrappedValue<UnwrappedType>() -> UnwrappedType {
-            return value as! UnwrappedType
-        }
-    }
-
-    public init() {}
-
-    public func sectioned(items: [Item]) -> (sections: [[Item]], collation: UILocalizedIndexedCollation) {
-        let collation = UILocalizedIndexedCollation.current()
-        let selector = #selector(getter: CollationWrapper.indexedOn)
-
-        let wrappedItems = items.map { item in
-            CollationWrapper(value: item, indexedOn: item.indexedOn)
-        }
-
-        let sortedObjects = collation.sortedArray(from: wrappedItems, collationStringSelector: selector) as! [CollationWrapper]
-
-        var sections = collation.sectionIndexTitles.map { _ in [Item]() }
-        sortedObjects.forEach { item in
-            let sectionNumber = collation.section(for: item, collationStringSelector: selector)
-            sections[sectionNumber].append(item.unwrappedValue())
-        }
-
-        return (sections: sections.filter { !$0.isEmpty }, collation: collation)
-    }
-}
-
-extension Contact: IndexableItem {
-    public var indexedOn: NSString {
-        guard let nickname = nickname else {
-            return "\(username!.first!)" as NSString
-        }
-
-        return "\(nickname.first!)" as NSString
-    }
-}