custom_profile_fields: Display success status after add/edit fields.
custom_profile_fields: Display success status after add/edit fields.

Display success status "Saved" for consistency in settings UI, after
successful request of Add or Edit custom profile fields.

Follow-up: #21878

andersk/zulip,zulip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,rht/zulip,zulip/zulip,andersk/zulip,rht/zulip,andersk/zulip,rht/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,rht/zulip,rht/zulip,andersk/zulip,rht/zulip,rht/zulip,zulip/zulip