new(cmd): add artifact config command

[alacuku]

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

/kind flaky-test

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area library

/area cli

/area tests

/area examples

What this PR does / why we need it:

Add a new command for artifacts: falcoctl artifact config which fetches the config layer for a given artifact.

❯ falcoctl artifact config falco-rules | jq
{
  "name": "falco-rules",
  "version": "2.0.0",
  "requirements": [
    {
      "name": "engine_version",
      "version": "26"
    }
  ]
}

Which issue(s) this PR fixes:
#332

Fixes #
#332
Special notes for your reviewer:

[alacuku]

/hold until we merge #339

[loresuso]

Pretty useful! I like it!

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: 141a72ac74ea0e69517795d7de49844f6c4344b1

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[FedeDP]

No conflict? can we unhold?

[alacuku]

/unhold