#4621 Add revision time on presave.

[swirtSJW]

Fixes #4621

Describe your changes

This explicitly sets data node revision time so that programatic changes like publish reflect the time of the publish, and don't repeat the time of the draft.
This results in revisions that look like

as opposed to the current situation of

QA Steps

• git checkout 4621-set-revision-date-4
• Save a dataset as draft.
• publish it using either a drush command or a bulk operation in the UI.
• Visit the revisions tab for the dataset. validate that the first line for each of the recent revisions has its own date and time. (rather than repeating the time.)
• validate that the revision message, which also looks like a time stamp did not change should still say something like "Created on " and the date should match the message from the draft revision.

Checklist before requesting review

If any of these are left unchecked, please provide an explanation

• I have updated or added tests to cover my code
• I have updated or added documentation

[swirtSJW]

Proof of working

[dafeder]

@swirtSJW where are these programatic revisions happening? If in DKAN core, it seems like the revision time should be set at the place in the code where the new revision is being created, not later in a hook?

[swirtSJW]

Closing this in favor of #4755