Add trending track last completion to health check

[raymondjacobson]

Description

What is the purpose of this PR? What is the current behavior? New behavior? Relevant links (e.g. Trello) and/or information pertaining to PR?

Add a health check field for the last time trending indexed.

I thought a bunch about where to put this -- options being:

1. health check
2. new trending_check
3. play_check

I ultimately felt that 1 would be the best even if we decide that clients dont need it near term to decide how to select because it gives us the ability to keep track of it in segment and it really shouldn't be expensive

Tests

List the manual tests and repro instructions to verify that this PR works as anticipated. Include log analysis if possible.
❗ If this change impacts clients, make sure that you have tested the clients ❗

1. Local setup

...

❗ Reminder 💡❗:
If this PR touches a critical flow (such as Indexing, Uploads, Gateway or the Filesystem), make sure to add the requires-special-attention label. Add relevant labels as necessary.