Makes several changes to consolidate snapshot and backup-related docs.
Highlights:
* Adds info about supported ESS snapshot repository types
* Adds docs for Kibana's Snapshot and Restore feature
* Combines tutorial pages related to taking and managing snapshots
* Consolidates explanations of the snapshot process
* Incorporates SLM into the snapshot tutorial
* Removes duplicate "back up a cluster" pages
* [DOCS] Combining important config settings into a single page (#63849)
* Combining important config settings into a single page.
* Updating ids for two pages causing link errors and implementing redirects.
* Updating links to use IDs instead of xrefs.
