Allow custom sort order per homepage section
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## Problem to Solve
Currently each section in the merge request list has a pre-defined sort order. While we've tried to optimize this, people will have different preferences for different lists. For example, some users would want to sort the `review requested` list by "when the request is made", and some may prefer "last updated".
## Proposal
We should introduce some kind of configuration on a per section basis that allows users to specify the sort order they want to use for each of the lists.
issue