Use Snowplow to track clicks on "Jump To Next" MR buttons

What does this MR do?

For #199458 (closed)

Adds click-tracking data-* attributes (so that Snowplow can pick up the custom events) to the Jump to Next Discussion buttons on the MR changes tab.

Screenshots

N/A (~backstage)

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

Availability and Testing

Previous notes on testing

Notable!

I chose not to add any new tests to this feature.
I did update the Jest snapshot to expect the new attributes, but otherwise everything is left alone.

I opted for this because the Snowplow JS is already looking for these attributes.
Any tests in this feature for whether Snowplow is picking up the clicks or whether Snowplow is sending the reporting feel like they're testing something in a much broader scope.

In any case, it would seem that Snowplow (and our JS integration) is tested fairly thoroughly in spec/frontend/tracking_spec.js.

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team