Support site_intent for /me/sites endpoint

[arthur791004]

Summary:
As we need to show different support articles according to the site intent, add site_intent into options list so that we can query from the /me/sites endpoint

Related to Automattic/wp-calypso#58486

Test Plan:

1. Go to API Console
2. Select WP.COM API > v1.2
3. Use /me/sites?fields=options&options=site_intent
4. Check the response of sites contains site_intent

Also, you can follow the testing instructions from Automattic/wp-calypso#58486

Reviewers: #ganon_team, philipmjackson

Reviewed By: #ganon_team, philipmjackson

Subscribers: philipmjackson

Tags: #touches_jetpack_files

Differential Revision: D70637-code

This commit syncs r235663-wpcom.

Fixes #

Changes proposed in this Pull Request:

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Go to '..'

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