feat(design): remove DaffArticleTitleDirective and DaffArticleLeadDirective and set styles directly on <h1> and first <p> of an article

[xelaint]

PR Checklist

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

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] 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?

You must use daffArticleTitle and daffArticleLead selectors in order to apply title and lead styles to an article.

Fixes: #2848

What is the new behavior?

Remove the directives and update styles to be applied to the <h1> of a <daff-article> and the first <p> that comes after a <h1>

Does this PR introduce a breaking change?

[x] Yes
[ ] No

BREAKING CHANGE:

DaffArticleTitleDirective and DaffArticleLeadDirective have been removed. The styles from these directives will automatically apply to the <h1> and first <p> that comes after a <h1> in a <daff-article>.

Other information