New Onboarding: check if site is on a paid plan to determine the action of editor Launch button

[razvanpapadopol]

This is a follow up of #47493

In order to redirect to Calypso launch flow when clicking Launch in the editor for a site with a paid plan active, we need to get data about having a paid active plan to ETK in https://github.com/Automattic/wp-calypso/blob/master/apps/editing-toolkit/editing-toolkit-plugin/editor-gutenboarding-launch/index.ts#L92

This can be achieved in 2 ways:
A. pass the data through iframe as suggested in #47493 (comment)
B. get the data directly from Site data-store