Disable editors welcome guides in global setup

[Marianne380]

Following https://github.com/polylang/polylang-pro/pull/2984#discussion_r3050662642.

What

Set welcomeGuide, welcomeGuideTemplate (core/edit-post) and welcomeGuide (core/edit-widgets) to false in global.setup.js via a REST call to PUT /wp/v2/users/me.

Why

Several specs across Polylang Pro and Polylang were dismissing the block editor and widget editor welcome guides inline, either via editor.setPreferences() or by clicking the close button.

Moving this to global setup removes the need to handle it in each spec.

How

The REST call is placed after the Promise.all() block.

This is intentional: resetPreferences() runs inside that block and makes a PUT /wp/v2/users/me with persisted_preferences: {}, which would overwrite our values.

[Hug0-Drelon]

Do you think it worths adding following preferences for core/edit-site?

{
	welcomeGuide: false,
	welcomeGuideStyles: false,
	welcomeGuidePage: false,
	welcomeGuideTemplate: false,
}

Also, there is fullscreenMode preference, do you think we should set it to a standard value for our e2e tests.

[Marianne380]

See 2612d49 and 8549c53.

Added core/edit-site preferences, no current spec covers the site editor but might as well cover it now.

fullscreenMode added too.