test(propagation): refactor setupShares in EtagPropagationTest

[joshtrichards]

• Resolves: #

Summary

• Descriptive, unique share variables
• All share acceptances grouped in each user's section
• Order and comments clarified
• No change to logic -- only improved readability and maintainability (though this I did start on this because of test flakiness from the FileInfo asserts in this function)

TODO

• ...

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)