Docs: Sync the BYOC doc with blog and update BentoCloud guides index page

[Sherlock113]

What does this PR address?

1. Sync the messaging in the BYOC doc with the BYOC blog post: https://www.bentoml.com/blog/byoc-to-bentocloud-privacy-flexibility-and-cost-efficiency-in-one-package
2. Update the BentoCloud guides index page

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