feature(storage): config support for generate section

[joseivanlopez]

Add support to the storage config for using a generate section for partitions and logical volumes.

{
  "partitions": [
    { "generate": "default" }
  ]
}

{
  "logicalVolumes": [
    {
      "generate": {
        "logicalVolumes": "mandatory",
        "stripes": 8
      }
    },
    {
      "filesystem": { "path": "swap" },
      "size": "8 GiB"
    }
  ]
}

• The generate section is replaced by the default or mandatory volumes defined by the product.
• If any volume is explicitly indicated in any device, then that volume is not added again by the generate section.

[coveralls]

coverage: 72.152%. remained the same
when pulling 0a2922d on joseivanlopez:storage-volume-keywords
into 1e736e3 on openSUSE:master.

[coveralls]

Pull Request Test Coverage Report for Build 11182376605

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 70.324%

---

Files with Coverage Reduction	New Missed Lines	%
rust/agama-cli/src/main.rs	6	0.0%

Totals
Change from base Build 11070850022:	-0.1%
Covered Lines:	15640
Relevant Lines:	22240

---

💛 - Coveralls

[ancorgs]

LGTM