Beta badge inner visual alignment

[ek-so]

Summary

• Current EuiBetaBadge looks slightly unbalanced in terms of text baseline: the label with uppercase letters by nature feels like being shifted a bit more towards the top of the badge, so I pulled it down very slightly.
• It also looks a bit too harsh when the text inside is bold, so I tried what if we make it semibold, and increase the font-size for smaller badge at the same time for better readability. This also makes the text better visually balanced with icon-only badge in terms of the line thickness.
  

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_8255/
• Storybook: https://eui.elastic.co/pr_8255/storybook
• New docs: https://eui.elastic.co/pr_8255/new-docs

[elasticmachine]

💚 Build Succeeded

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• Commit: 368a487

[ek-so]

Hey team, before reviewing from a technical side I'd like to ask somebody from design side to check the visual part and my considerations. @MichaelMarcialis @ryankeairns what are your thoughts?