settings: Fix external account profile field initialization order.
settings: Fix external account profile field initialization order.

In open_edit_form, we had an initialization order bug where we called
set_up_external_account_field_edit_form, which clears the field name
field if the external account is of the "custom" type, after
populating the initial values for edit form.

This resulted in these fields being displayed as empty in the UI for
this field type. Fix the issue by reordering the initialization.

Fixes: #21262.

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