Handle multiple entries in the DAST report artifact, Add specs for legacy DAST report

What does this MR do?

Iterate through the entire site array to parse the DAST report artifact instead of just considering the first element.

Pending items:

• Add specs (Will be done post !17778 (merged))
• Adds specs for legacy DAST report (#33030 (closed))

Related to #11930 (closed)

Related to #33030 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content