settings: Use user-level email_address_visibility setting in UI.

This commit basically updates the frontend code to directly use
delivery_email field instead of functions like show_email or
email_for_user_settings at places where we want to show email.
We can do this change since we recently updated the server code
to always pass "delivery_email" code in the user objects with its
value being null if the real email is not accessible.

Showing email or "hidden" or nothing at various places in UI like
in users list, subscriber list, user profile popover and modal is
same as before.

Major points -

- Removed show_email and email_for_user_settings functions since we
directly use delivery_email field now as explained above.

- While sorting by emails in the users list, users with real emails
hidden are always shown in last when sorting alphabetically and at
the top when sorting reverse alphabetically. Also, those users with
real emails hidden, are sorted by name among themselves. As we did
before, we do not allow sorting by email when all emails are hidden.

- There is no change in typeahead behavior at this point. We either
hide the email completely or show the real or fake email based on
user level setting.

- Added code to handle delivery_email events and appropriately add/remove
delivery_email field from person objects.

static/js/settings_users.js

@@ -20,7 +20,6 @@ import * as presence from "./presence";
 import * as settings_account from "./settings_account";
 import * as settings_bots from "./settings_bots";
 import * as settings_config from "./settings_config";
-import * as settings_data from "./settings_data";
 import * as settings_panel_menu from "./settings_panel_menu";
 import * as timerender from "./timerender";
 import * as ui from "./ui";
@@ -42,8 +41,22 @@ function compare_a_b(a, b) {
 }
 
 function sort_email(a, b) {
-    const email_a = settings_data.email_for_user_settings(a) || "";
-    const email_b = settings_data.email_for_user_settings(b) || "";
+    const email_a = a.delivery_email;
+    const email_b = b.delivery_email;
+
+    if (email_a === null && email_b === null) {
+        // If both the emails are hidden, we sort the list by name.
+        return compare_a_b(a.full_name.toLowerCase(), b.full_name.toLowerCase());
+    }
+
+    if (email_a === null) {
+        // User with hidden should be at last.
+        return 1;
+    }
+    if (email_b === null) {
+        // User with hidden should be at last.
+        return -1;
+    }
     return compare_a_b(email_a.toLowerCase(), email_b.toLowerCase());
 }
 
@@ -82,6 +95,15 @@ function get_user_info_row(user_id) {
     return $(`tr.user_row[data-user-id='${CSS.escape(user_id)}']`);
 }
 
+export function allow_sorting_deactivated_users_list_by_email() {
+    const deactivated_users = people.get_non_active_realm_users();
+    const deactivated_humans_with_visble_email = deactivated_users.filter(
+        (user) => !user.is_bot && user.delivery_email,
+    );
+
+    return deactivated_humans_with_visble_email.length !== 0;
+}
+
 export function update_view_on_deactivate(user_id) {
     const $row = get_user_info_row(user_id);
     if ($row.length === 0) {
@@ -236,7 +258,7 @@ function human_info(person) {
     info.can_modify = page_params.is_admin;
     info.is_current_user = people.is_my_user_id(person.user_id);
     info.cannot_deactivate = info.is_current_user || (person.is_owner && !page_params.is_owner);
-    info.display_email = settings_data.email_for_user_settings(person);
+    info.display_email = person.delivery_email;
 
     if (info.is_active) {
         // TODO: We might just want to show this
@@ -451,7 +473,7 @@ export function confirm_deactivation(user_id, handle_confirm, loading_spinner) {
             const realm_name = page_params.realm_name;
             const opts = {
                 username: user.full_name,
-                email: settings_data.email_for_user_settings(user),
+                email: user.delivery_email,
                 bots_owned_by_user,
                 number_of_invites_by_user,
                 admin_email: people.my_current_email(),
@@ -574,11 +596,9 @@ export function show_edit_user_info_modal(user_id, from_user_info_popover) {
         return;
     }
 
-    const user_email = settings_data.email_for_user_settings(person);
-
     const html_body = render_admin_human_form({
         user_id,
-        email: user_email,
+        email: person.delivery_email,
         full_name: person.full_name,
         user_role_values: settings_config.user_role_values,
         disable_role_dropdown: person.is_owner && !page_params.is_owner,