Always use Jetpack_Options::get_option( ‘id’ )

Until recently, WP.com wouldn't return the correct site id when it called `Jetpack_Options::get_option( ‘id’ )`. Instead we'd have to add lots of this in the code:

```
if ( IS_WPCOM ) { return get_current_blog_id() } else { Jetpack_Options::get_option( 'id' ) }
```

However since #16561, we can use Jetpack_Options::get_option( 'id' ) on WP.com as well as self-hosted Jetpack sites, so we can remove all of these forks in the code. See also p9dueE-1Ee-p2

- [ ] https://github.com/Automattic/jetpack/blob/092d9af6c96384083ae509741be77a8db9346721/_inc/lib/core-api/wpcom-endpoints/class-wpcom-rest-api-v2-endpoint-mailchimp.php#L78
- [ ] https://github.com/Automattic/jetpack/blob/874e9fd02381364cfc7bb4307a055faf930dc5e2/_inc/lib/core-api/wpcom-endpoints/class-wpcom-rest-api-v2-endpoint-search.php#L52
- [ ] https://github.com/Automattic/jetpack/blob/d37c4eca5842ca81a9f0c368fad1b0b83561acef/_inc/lib/class-jetpack-mapbox-helper.php#L88
- [ ] https://github.com/Automattic/jetpack/blob/a1fe6f0b03ea68fb5e0eed1e22d585e2351b2a06/_inc/lib/class-jetpack-instagram-gallery-helper.php#L105
- [ ] https://github.com/Automattic/jetpack/blob/ebec0a8fb35ffac4766cce36646ebf01c5d56063/modules/videopress/class.videopress-gutenberg.php#L133
- [ ] https://github.com/Automattic/jetpack/blob/d37c4eca5842ca81a9f0c368fad1b0b83561acef/modules/tiled-gallery/tiled-gallery/tiled-gallery-layout.php#L91
- [ ] https://github.com/Automattic/jetpack/blob/ea7625a3f46e9e9a100722d23ea33b4c610929b4/_inc/lib/core-api/wpcom-fields/attachment-fields-videopress.php#L66
- [ ] https://github.com/Automattic/jetpack/blob/60f0fa1db582116753d24a49446dc7e70c219f76/modules/memberships/class-jetpack-memberships.php#L344
- [ ] https://github.com/Automattic/jetpack/blob/b7acf5e41bfb344969b409fc61c884a955e785a2/modules/likes.php#L224
- [ ] https://github.com/Automattic/jetpack/blob/ebec0a8fb35ffac4766cce36646ebf01c5d56063/extensions/blocks/mailchimp/mailchimp.php#L55
- [ ] https://github.com/Automattic/jetpack/blob/da783ccfb0173804d37797031bb87d7c9bc1f794/modules/simple-payments/simple-payments.php#L113
- [ ] https://github.com/Automattic/jetpack/blob/9a437395f0d2f8248bea436faacd8445e71de846/_inc/lib/class-jetpack-tweetstorm-helper.php#L1677

Start with the twelve linked PHP files and inspect each conditional that chooses between get_current_blog_id() and Jetpack_Options::get_option('id'). Update the listed call sites so they consistently use the option lookup, then confirm every checklist item has been addressed and the existing behavior remains correct for WP.com and self-hosted Jetpack sites.

Written by the indexing model from the issue text.