Bundled Themes: Accessibility additions to the site title link

[bschneidewind]

In bundled themes, adds the aria-current="page" (when applicable) and rel="home" to the site title link. The approach varies depending on how the theme is structured.
Updates:
TwentyTen
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Trac ticket: https://core.trac.wordpress.org/ticket/62895

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[github-actions]

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