moved ConversationsSortFilterProxyModel class from conversationlistmodel files to its own files
Summary
Currently OurSortFilterProxyModel
class is implemented in the same file with ConversationListModel
class, which would likely grow in the future.
This MR separates OurSortFilterProxyModel
class into its own separate file renaming it to ConversationsSortFilterProxyModel
Edited by Aniket Kumar