SLO docs overhaul

[apoorv-garg]

Purpose of this pull request

• Reordering of sections on create slo page.
• Removed the duplicate documentation for sumologic_slo_output and lookup table from create slo page.
• Removed SLO use cases page. It has old queries and just reconstructs existing panels, which is already covered in SLO dashboard page docs.
• Improvements to SLO dashboard page

Select the type of change:

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions and updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - Updates, maintenance, and new packages for the site, Gatsby, React, etc

[cla-bot]

Thank you for your contribution! As this is an open source project, we require contributors to sign our Contributor License Agreement and do not have yours on file. To proceed with your PR, please sign your name here and we'll add you to our approved list of contributors.

[cla-bot]

Thank you for your contribution! As this is an open source project, we require contributors to sign our Contributor License Agreement and do not have yours on file. To proceed with your PR, please sign your name here and we'll add you to our approved list of contributors.

[cla-bot]

Thank you for your contribution! As this is an open source project, we require contributors to sign our Contributor License Agreement and do not have yours on file. To proceed with your PR, please sign your name here and we'll add you to our approved list of contributors.

[kimsauce]

Excellent job, @apoorv-garg ! Thanks so much for doing. Just had some minor formatting suggestions.

[apoorv-garg]

Excellent job, @apoorv-garg ! Thanks so much for doing. Just had some minor formatting suggestions.

Thanks for the suggestions, applied.