Add metric for page load

What does this MR do and why?

This MR adds tracking when the training material is loaded. This does not introduce any UI/UX changes.

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.

Related to #348593 (closed)