Apply Product Intelligence feedback to existing Snowplow events definitions

What does this MR do and why?

Related to #333992 (closed)

This MR addresses the feedback left on !67981 (merged) for the files not part of that MR.

• Prepend filenames with the file creation timestamp
• Update distributions to be consistent with service ping metrics definitions. CE definitions should be available in all tiers. EE definitions are not available on CE/free.
• Prepend group:: to the product_group field.

This is a significant MR, but the changes are easy to comb through.

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.