Adds tracking to the Post List Share option

[emilylaguna]

Project: #17503

Description

Adds tracking when you tap the 'Share' option from the More menu on the post list view

To test:

Filter Sheet

1. Launch the app
2. Tap on My Site
3. Tap on Posts
4. Tap the ⋯ More button
5. Tap the Share item
6. Verify you see: 🔵 Tracked: post_list_button_pressed <blog_id: BLOG_ID, button: share, filter: Published, type: post>

Regression Notes

1. Potential unintended areas of impact
   None, adding tracking.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Manual testing

3. What automated tests I added (or what prevented me from doing so)
   None.

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]

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

[frosty]

Looks good!