[Security] Visual event analyzer updates (#2606)

Resolves #2339 by updating
the Visual event analyzer docs to reflect the latest UI. This PR also
reduces the number of screenshots on the page, for easier maintenance.

Preview: [Visual event
analyzer](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/2606/solutions/security/investigate/visual-event-analyzer)

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Co-authored-by: Mike Birnstiehl <[email protected]>

Author: natasha-moore-elastic