Room mentioning in the composer (#3868)

* refactored the suggestion item structure

to scale with the room pill

* Implemented a way for the rooms

to appear in the suggestions view for the RTE, however I need to add the pills to the composer and the compatibility with the plain text composer

* small code correction

* fix

* fixed a bug where the suggestion wasn't returning

the right suggestion type and the suggestion text properly

* implementation done!

also updated some tests, but we need more of them

* updated toolbar view model tests

* updated tests

* updated preview tests

* renamed the Avatars case for the suggestions

ElementX/Sources/Mocks/RoomSummaryProviderMock.swift

@@ -197,7 +197,7 @@ extension Array where Element == RoomSummary {
                     unreadMentionsCount: 0,
                     unreadNotificationsCount: 0,
                     notificationMode: .mute,
-                    canonicalAlias: nil,
+                    canonicalAlias: "#prelude-foundation:matrix.org",
                     alternativeAliases: [],
                     hasOngoingCall: true,
                     isMarkedUnread: false,