feat(decl/resources): adds fd test resource and test resource builder

[ekoops]

What type of PR is this?

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/kind bug

/kind cleanup

/kind documentation

/kind tests

/kind feature

Any specific area of the project related to this PR?

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/area commands

/area pkg

/area events

What this PR does / why we need it:
This PR adds the fd test resource, the test resource builder and fixes some minor issues related to YAML specs validation. The fd test resource is a resource that lets the user declaratively create one file descriptor (or more, in case of pipe) . The user must specify the fd type using the subtype YAML field. The following subtypes have been introduced:

• file
• directory
• pipe
• event
• signalfd
• eventpoll
• inotify
• memfd

Depending on the selected subtype more attributes could be required to completely specify the fd test resource. For instance, the following is the YAML declaration of a directory fd test resource:

    ...
    resources:
      - type: fd
        name: directory1
        subtype: directory
        dirPath: "/path/to/dir"
    ...

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

[leogr]

/kind feature

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: b319bde95bfdd2dcf1affc840119ec2704b44d9d

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ekoops, FedeDP

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