Label tooltip on filepath of diffs to the action that will happen

Proposal

Originally discussed in !195610 (comment 2589802236)

1. For diffs on the Overview, clicking on the filepath will take you to the Changes tab
2. For diffs on the Changes tab, clicking on the filepath will open a new tab and take you to the file
   • This was the change made in Put link to a blob in the diff file title (!195610 - merged)

Proposed change is to have a tooltip to inform the user of the action that is going to be taken

1. For diffs on the Overview: Go to file diff in Changes
2. For diffs on the Changes tab: View file @ SHA

Currently the tooltip on the filepath say what the name of the file path is. This filepath doesn't get truncated so we are not losing existing functionality