Initial support for sorting storage devices during the search

[ancorgs]

Problem

The results of the search section in the description of drives, partitions and mdRaids are always sorted by name. Making it very hard to specify something like "the two biggest disks".

Solution

This implements support for implementing such searches with the syntax shown in the following examples:

{
  "search": {
    "sort": { "size": "desc" },
    "max": 2
  }
}

Several criteria can be specified to resolve ties.

{
  "search": {
    "sort": [
        { "size": "desc" },
        "name"
    ],
    "max": 2
  }
}

And, of course, all that can be combined with a condition to filter out devices before sorting.

{
  "search": {
    "condition": { "size": { "less": "1TiB" } },
    "sort": { "size": "desc" },
    "max": 2
  }
}

Testing

• Added unit tests for the new parts
• Tested manually

[coveralls]

coverage: 62.527% (+0.1%) from 62.407%
when pulling 7b69732 on ancorgs:search_sort
into 1495361 on agama-project:master.

[joseivanlopez]

LGTM