Remove full-width trick pending better one

This also adds a few improvements from the now deleted branch, #799, notably:

- clearing for video blocks. The responsive trickery means we have to, or we will get odd behavior otherwise
- better collapsing margins fix for the toolbar.

blocks/library/embed/style.scss

@@ -1,6 +1,7 @@
 .blocks-embed,
 .blocks-embed-video {
 	margin: 0;
+	clear: both;	// necessary because we use responsive trickery to set width/height, and therefore the video doesn't intrinsically clear floats like an img does
 }
 
 .blocks-embed-video > div:first-child {

editor/modes/visual-editor/style.scss

@@ -18,8 +18,7 @@
 	}
 }
 
-/* "Hassle-free full bleed" from CSS Tricks */
-.editor-visual-editor > *:not( [data-align="wide"] ) {
+.editor-visual-editor {
 	max-width: $visual-editor-max-width;
 	margin-left: auto;
 	margin-right: auto;
@@ -101,16 +100,12 @@
 	}
 }
 
+$sticky-bottom-offset: 20px;
 .editor-visual-editor__block-controls + div {
-	margin-top: -20px;
-
-	// prevent collapsing margins between the block and the toolbar
-	&:before {
-		content: "";
-		display: table;
-		clear: both;
-	}
-}
+	// prevent collapsing margins between block and toolbar, matches the 20px bottom offset
+ 	margin-top: -$sticky-bottom-offset - 1px;
+	padding-top: 1px;
+ }
 
 .editor-visual-editor__block-controls .components-toolbar {
 	display: inline-flex;