Revert email_* calls to not use generic API

It is undesirable to use this approach for the following:

• Having each caller having to know the right language string + call type.
• Having a properly named APIs provides better intelli-sense experience.
• It is easier to add event spent logic or extra parameters compared to switch statements in generic API.
• More inline with the approach of having different email formats based on the change event, rather than a single format which dumps the whole issue, rather than focus on the actual change.

Fixes 0019984

This reverts commit 03c5a5d18cfef07dec45a1025072981f24a5f07c.

Conflicts:

• bug_update.php
• core/bugnote_api.php
• library/disposable
• library/ezc/Base
• library/ezc/Graph
• library/securimage