[Docs migration] Cleans up getting started files - Pt. 1 (#497)

Addresses part of #559 by
doing the following:
- Removes raw migrated Serverless files (content and some images) that
are no longer being used.
- Adds anchors where missing and updates anchors that start with an
underscore.
- Makes minor inline adjustments to the files that were labeled as
"lift-and-shift" where appropriate.

Affected pages:
- [Configure advanced
settings](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/497/solutions/security/get-started/configure-advanced-settings)
- [Data views and Elastic
Security](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/497/solutions/security/get-started/data-views-elastic-security)
- [Ingest data into Elastic
Security](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/497/solutions/security/get-started/ingest-data-to-elastic-security)

---------

Co-authored-by: Benjamin Ironside Goldstein <[email protected]>

Author: nastasha-solomon