Consensus Banana Phase 1, cleanup

Adding this as a follow up. I just wanted a place to put preprocess functions we might have missed in the other issues. They can all be done in one patch, if at all, since there don't seem to be many. This will, hopefully, be the last issue fixed, which would mean phase 1 is complete.

This is what I see so far from searching:

core/includes/menu.inc
template_preprocess_menu_local_task
template_preprocess_menu_local_action (the attributes go into a #type link render array)

core/includes/theme.inc
template_preprocess_datetime_form
template_preprocess_html (db_is_active is available at the template so we might be able to move that db-offline class.)
template_preprocess_field_multiple_value_form (all classes are used to build a #type table render array)

core/modules/file/file.field.inc
template_preprocess_file_widget_multiple (all classes are used to build a #type table render array)

core/modules/file/file.module
template_preprocess_file_managed_file (form-managed-file is required for JS)

These may end up not needing a fix. Discuss/analyze and strike it out if it doesn't need a fix. If a new one is found, add it to the summary.

Suggested commit message:
Issue #2407565 by davidhernandez, brianperry, lauriii: Consensus Banana Phase 1, cleanup