Promote "history sharing on invite" out of developer options (#5480)

* Enable key-share-on-invite irrespective of feature flag

* Remove feature-flag dep: warning on starting chat with new people

* Remove feature-flag dep: invite from room member details

* Remove feature-flag dep: warning on new users in invite screen

* Remove feature-flag dep: from room details screen

* Remove feature-flag dep: starting chat from user profile screen

* Remove feature-flag dep: timeline info on forwarded keys

* Remove feature-flag dep: RoomScreenModel

* Remove `enableKeyShareOnInvite` from AppSettings

* Remove `enableKeyShareOnInvite` feature flag

* Remove outdated comments

* Update preview test room snapshots as their header now includes the history sharing icon

NSE/Sources/NSEUserSession.swift

@@ -73,7 +73,6 @@ final class NSEUserSession: NSEUserSessionProtocol {
                          sessionDelegate: clientSessionDelegate,
                          appHooks: appHooks,
                          enableOnlySignedDeviceIsolationMode: appSettings.enableOnlySignedDeviceIsolationMode,
-                         enableKeyShareOnInvite: appSettings.enableKeyShareOnInvite,
                          requestTimeout: 15000,
                          maxRequestRetryTime: 5000,
                          threadsEnabled: appSettings.threadsEnabled)