Auth: update generic OAuth documentation (#70330)
* update generic OAuth docs
* update examples and sync sections
* formatting and adding more links to OAuth integrations
* add a section with config walkthrough
* move examples to the end of the doc
* extend role mapping
* add a before you begin section, clean up steps, remove some text
* remove unnecessary section
* OAuth -> OAuth2
* remove Centrify example because it's likely outdated
* add shared intro content
* add refresh token to tasks, clean up more sections
* Update docs/sources/setup-grafana/configure-security/configure-authentication/generic-oauth/index.md
* indentation and small descriptions under headings
* add a table for config options
* clean up more sections
* rewrite email address section
* rewriting login and display name sections, plus adding line breaks
* update role mapping section
* update section names
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Co-authored-by: Christopher Moyer <35463610+chri2547@users.noreply.github.com>
(cherry picked from commit 276c63a656)
Co-authored-by: Ieva <ieva.vasiljeva@grafana.com>
907445beef