Fixes #24097: Skipped directive does not show in node compliance tree

[clarktsiory]

https://issues.rudder.io/issues/24097

Essentially the same as #5600, and with some refactoring :

• move the Elm model for SkippedDirective to the Elm Compliance.Datatypes module
• compute the skipped directives in a method which takes the conversion DirectiveComplianceOverride => T as a param, either ByRuleDirectiveCompliance or ByRuleDirectiveCompliance (this PR)

[fanf]

So, the code looks good and we now have skipped in node, but I still think there is something broken: in the case where the rule has only one directive and that directive is skipped, then the rule doesn't appear at all in the node.

Step to reproduce: in your screenshot example, remove the directive "File download (HTTP)" from rule "Install package skip"