feat(design)!: change `daffSkeletonMixin` to a directive

PR Checklist

Please check if your PR fulfills the following requirements:

[x] The commit message follows our guidelines: https://github.com/graycoreio/daffodil/blob/develop/CONTRIBUTING.md#commit
[x] Tests for the changes have been added (for bug fixes / features)
[x] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

An ElementRef and Renderer need to be constructed for the daffSkeletonMixin to be extendable or usable in a component.

Part of: #2911

What is the new behavior?

Removed daffSkeletonMixin in favor of DaffSkeletonableDirective so that a component can use the directive by adding it as a hostDirective. This reduces code complexity.

Dependent on #2913, #2919, #2922 to be merged first.

Does this PR introduce a breaking change?

[x] Yes
[ ] No

BREAKING CHANGE: daffSkeletonMixin has been removed in favor of DaffSkeletonableDirective. Update usage by using the hostDirective feature.

graycoreio / daffodil