Merge some buttons into a Controls island

I know i am risking a tricky rebase when 📌 Island lighter base class Active will land but i am taking it anyway.

Let's keep the existing enabled_by_default behaviour:

• Toggle fullscreen: TRUE
• Toggle highlight: TRUE
• Keyboard help: FALSE
• Theme mode selector: FALSE

And the default config entity settings:

default:

• Toggle fullscreen: TRUE
• Toggle highlight: TRUE
• Keyboard help: TRUE
• Theme mode selector: FALSE

devel (in Dev Tools):

• Toggle fullscreen: TRUE
• Toggle highlight: TRUE
• Keyboard help: FALSE
• Theme mode selector: FALSE

Work in progress.

3 remaining tasks:

• Fix: boolean values not updated on island from submit
• Decide: What do we do with conditional keyboard_shortcuts ?
• Do: Related issue on Dev Tools

In the meantime related to 📌 More responsive toolbar Active , let's make it directly responsive with a dropdown.

In the meantime related to #3544782: More responsive toolbar, let's make it directly responsive with a dropdown.

OK, i will try include this in my MR.