Configuring and submitting an EActivity for every mail operation is
getting tedious. This function helps reduce boilerplate code by:
* Creating a new EActivity instance.
* Installing an EAlertSink using e_mail_reader_get_alert_sink().
* Installing a GCancellable (which is really a CamelOperation).
* Submitting the activity via e_shell_backend_add_activity().
I'm considering adding a similar function (or class method) for
EShellView. Not sure yet...
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