Add iconUrl check upon index component validation

[thepetk]

Please specify the area for this PR
registry/

What does does this PR do / why we need it:
Adds an iconUrl check inside the generator.library.validateIndexComponent func.
This way it blocks the build of the registry if an icon does not exist, or has an invalid url.

Which issue(s) this PR fixes:
devfile/api#1024

Fixes #?

PR acceptance criteria:

• Test Coverage
  • Are your changes sufficiently tested, and are any applicable test cases added or updated to cover your changes?

Documentation (WIP)

• Does the REST API doc need to be updated with your changes?
• Does the registry library doc need to be updated with your changes?

How to test changes / Special notes to the reviewer:

• Clone locally the devfile registry repo
• Edit the .ci/Dockerfile git clone command in order to clone the branch of my fork instead of the registry support repo. This way you will be able to test my build tools.
• Edit an iconUrl from one of the stack/samples and try to build an image of the registry repo locally.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (4bc237b) 43.20% compared to head (182a8df) 43.20%.

❗ Current head 182a8df differs from pull request most recent head e0484d8. Consider uploading reports for the commit e0484d8 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #167   +/-   ##
=======================================
  Coverage   43.20%   43.20%           
=======================================
  Files           6        6           
  Lines        1037     1037           
=======================================
  Hits          448      448           
  Misses        546      546           
  Partials       43       43           

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[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: kim-tsao, thepetk
Once this PR has been reviewed and has the lgtm label, please assign johnmcollier for approval. For more information see the Kubernetes Code Review Process.

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[openshift-ci]

New changes are detected. LGTM label has been removed.