feat(storage): initial version of config search

[joseivanlopez]

Allow using a search section in the storage JSON config for drives and partitions, according to the auto_storage document. For now, the search only supports:

• To search by device name (linux name or udev name).
• To fail or to skip the section if the device is not found.

Examples:

{
  "search": "/dev/disk/by-id/ata-Micron_1100_SATA_512GB_1652155452D8"
}

{
  "search": {
    "condition": { "name": "/dev/vdc1" },
    "ifNotFound": "skip"
  }
}

[coveralls]

coverage: 71.68%. remained the same
when pulling d957ad4 on joseivanlopez:storage-search
into 4cabf6c on openSUSE:master.

[joseivanlopez]

The document auto_storage suggests two possible syntaxes for the search condition:

Option A:

{
  "search": {
    "condition": { "property": "name", "value": "/dev/sda2" }
  }
}

Option B:

{
  "search": {
    "condition": { "name": "/dev/sda2" }
  }
}

The option B was chosen in this PR because the following reasons:

• It is shorter and more expressive.

{"size": { "greater": "1 GiB" } } vs
{ "property": "size", "value": "1 GiB", "operator": "greater" }

• It is easier to validate the possible properties and their values in the schema.

• It is easier to define different sets of searches in the schema. For example, a drive could be searched by name, size and model, but a partition only by name and size.

[joseivanlopez]

There is a third option to be discussed. It consists on directly use the condition without wrapping with a condition property:

{
  "search": {
    "name": "/dev/vda1",
    "ifNotFound": "skip"
  }
}

{
  "search": {
    "and": [
      { "size": { "greater": "10 GiB"} },
      { "size": { "less": "50 GiB"} }
    ]
  }
}

[imobachgs]

LGTM