Update Semantic Layer Guide

[gwenwindflower]

What are you changing in this pull request and why?

The SL Best Practices guide was due for some updates, as well as bringing in some new content from the Data team's learnings and best practices they've developed in implementing the SL.

Checklist

• [x] Review the Content style guide so my content adheres to these guidelines.
• [x] For docs versioning, review how to version a whole page and version a block of content.
• [x] Add a checklist item for anything that needs to happen before this PR is merged, such as "needs technical review" or "change base branch."

Adding or removing pages (delete if not applicable):

• [x] Add/remove page in website/sidebars.js
• [x] Provide a unique filename for new pages
• [x] Add an entry for deleted pages in website/vercel.json
• [x] Run link testing locally with npm run build to update the links that point to deleted pages

[vercel[bot]]

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Name	Status	Preview	Comments	Updated (UTC)
docs-getdbt-com	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jun 27, 2024 5:47pm

[mirnawong1]

@gwenwindflower added teh trigger_crawl label so algolia search indexes this!

[gwenwindflower]

@nataliefiann @mirnawong1 these edits are awesome, ty!!! ❤️

[mirnawong1]

fixed error: https://vercel.com/dbt-labs/docs-getdbt-com/EBJcjRXGt3bHEmhVfehhvZd7CHgp?filter=errors

[github-actions[bot]]

Check your created Crawler

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