Improve SharePoint Embedded documented authorization model (#10731)

* Remove Container.Selected references for SharePoint Embedded

The application permission "Container.Selected" on the SharePoint
resource is not required anymore. This change removes all refs
to this app permission in the authn & authz article.

* Add section for user permissions in SharePoint Embedded auth page

* fixup! Add section for user permissions in SharePoint Embedded auth page

* Clarify ManageContent container type permission

* Add note on membership types for SPE authz

* Reformat container permissions table

* Clarify that Owner can restore deleted containers

* Apply suggestion from @dluces

* docs: fix formatting and style issues in SPE auth article

- fix "Pre-Requisites" heading to "Prerequisites"
- bold first-column entries in permission tables
- fix extra whitespace on line 156
- replace "M365 group" with "Microsoft 365 group"

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Co-authored-by: Andrew Connell <me@andrewconnell.com>

Author: dluces