Comments: Add tracking for comment sharing intent

[dvdchr]

Refs #17475

As titled, adds tracking for comment share intents:

• reader_article_comment_shared when shared from the comment threads.
• site_comments_comment_shared when shared from Site Comments.

To test

Site comments

• Go to My Site > select any approved comments.
• Tap on the Share button.
• 🔍 Verify that this appears console: 🔵 Tracked: site_comments_comment_shared <>

Reader comments

• Enable the newCommentThread feature flag.
• Go to Notifications > select any comment notification.
• Tap on the notification header to go to the comment threads.
• Tap the share button (or if you can moderate, tap ellipsis button > Share).
• 🔍 Verify that this appears in the console: 🔵 Tracked: reader_article_comment_shared <>

Regression Notes

1. Potential unintended areas of impact
   Should be none.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Manually tested to ensure that the tracks are sent correctly.

3. What automated tests I added (or what prevented me from doing so)
   n/a.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

	Warnings
⚠️	This PR is assigned to a milestone which is closing in less than 4 days Please, make sure to get it merged by then or assign it to a later expiring milestone

Generated by 🚫 dangerJS

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[ScoutHarris]

👍