Update Browser Performance Testing templates to use SiteSpeed 14.1.0

What does this MR do?

Updates Browser Performance Testing templates to use SiteSpeed 14.1.0 and to track CPU metrics. Also updates Docs screenshot to show new metrics that will now be shown as part of gl-performance!7 (merged).

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content