Publicize: add Fediverse creator meta tag from Mastodon connection (#…

…38809)

* Publicize: add Fediverse creator meta tag from Mastodon connection

This is a follow-up to #38198, which was partially reverted in #38612.
It's an alternative to #38565, to ensure better compatibility with WordPress.com Simple.

1. It takes into account the ActivityPub plugin, and ensure we're not adding a tag when the ActivityPub plugin already adds one.
2. It takes into account that on WordPress.com Simple, `get_services()` may return a `Keyring_Access_Token` object instead of an array.
3. It adds the 2 necessary methods directly to the `functions.opengraph.php` file, since we know it is loaded on the frontend on WordPress.com Simple (see conversation here to find out more: Automattic/jetpack#38565 (comment) )

* Add missing since parameter

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/10357379297

Upstream-Ref: Automattic/jetpack@3c68c42