DFW v2: fix adding of the old DFW buttons and TinyMCE's fullscreen mode

[azaozz]

Assuming we are keeping the old DFW code for now but encouraging plugins that want to use it to "copy" it from core and implement it themselves. We can look at removing that code perhaps in the next WordPress version.

Plugins should be able to add the old DFW buttons easily, both for the "main" editor and for other instances. Also there are bugs when using the TinyMCE's fullscreen plugin in the "main" editor.

[azaozz]

In 30453.patch:

• Add CSS reset for the TinyMCE's fullscreen mode when used on the Edit Post screen.
• Fix loading of the new/old DFW's buttons, use another arg. passed to WP_Editors.
• Reset editor-expand when exiting TinyMCE's fullscreen mode.

[azaozz]

In 30573:

Editor:

• Add CSS reset for the TinyMCE fullscreen mode when used on the Edit Post screen.
• Fix loading of the old and new DFW buttons, use another arg. passed to WP_Editors.
• Reset editor-expand when exiting TinyMCE fullscreen mode.

Fixes #30453.

[azaozz]

In 30583:

Editor: fix warnings in class-wp-editor.php, see #30453.

[azaozz]

In 30594:

Editor: move the DFW v2 transitions CSS from editor.css to wp-admin.css. They are needed only on the Edit Post screen.
See #30453.