Site Settings: Convert checkboxes to toggles in the General tab

[tyxla]

This PR refactors the existing general settings to use toggles instead of checkboxes (see #9171). Inspired by @ryelle's awesome work in #10167. This work was previously done in #10209, but I had to begin from scratch because 90% of what I did was done there was done in #9085 (which was recently merged).

Screenshots

Jetpack Site

WordPress.com site

To test

• Get this branch going locally or on calypso.live.
• Visit the General settings at /settings/general/$site for a Jetpack site.
• Note that in order to see the post status sync option, you need Jetpack <= 4.1.1 on your Jetpack site.
• Make any changes to any of the toggles.
• Verify that all changes have been saved and applied to your Jetpack site.

Also, test on WordPress.com sites (it contains Language and Site Timezone options, as well as a Private option for the Privacy setting):

• Get this branch going locally or on calypso.live.
• Visit the General settings at /settings/general/$site for a WordPress.com site.
• Make any changes to any of the toggles.
• Verify that all changes have been saved and applied to your WordPress.com site (you can also check the production settings page).

/cc
@ryelle @oskosk @roccotripaldi @johnHackworth for code review
@rickybanister @MichaelArestad for design review

[matticbot]

Test live: https://calypso.live/?branch=update/site-settings-general-checkboxes-to-toggles

[oskosk]

This looks good to me but a few observations:

1. In the context of the new designs for settings, toggles are proposed to save as soon as they toggle.
   From p6TEKc-HQ-p2:

_When a toggle is used, it should immediately enable that thing and show a global notice to show status of enabling that thing.

2. This PR will make the General tab checkboxes consistent with the design of the other tabs, but we have no mention about how the General tab should look in p6TEKc-HQ-p2. We could use an opinion from @rickybanister about this.

[tyxla]

@oskosk the toggles were already approved from @rickybanister and @MichaelArestad in the other PR (#10209), so I think just a general design feedback is necessary on this one.

[oskosk]

Alirght!, then

[MichaelArestad]

In the context of the new designs for settings, toggles are proposed to save as soon as they toggle.

@oskosk is right about the functionality, but let's fix that in another PR. Looks good on design.

[tyxla]

Thanks for the quick review folks 👍