doc: Add Sec Analyzer Automated Flows blueprint

What does this MR do and why?

Adds draft blueprint for Sec Analyzers Automated Flows, see #368284 (closed)

This initial draft covers the primary challenges and goals. With further iterations we'll cover category boundarie and timelines

• DIY its-a-markdown-file review app: https://gitlab.com/gitlab-org/gitlab/-/blob/add-sec-analyzer-automated-flows-blueprint/doc/architecture/blueprints/sec_analyzer_automated_flows/index.md
• Per Evolutionary Architecture Workflow

Background

Sec section analyzers should include metadata on the outcomes of scans in order to inform report ingestion. See parent issue for further discussion.

This data can be used to direct the processing of reports for more efficient vulnerability management.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.