Switch from setupCustomHover to hoverService (microsoft#166500)

Ref microsoft#159088
By switching to hoverService, we get to customize the hover widget
more for the Settings editor indicators.

Author: rzhao271

src/vs/base/common/async.ts

@@ -819,7 +819,7 @@ export class IntervalTimer implements IDisposable {
 	}
 }
 
-export class RunOnceScheduler {
+export class RunOnceScheduler implements IDisposable {
 
 	protected runner: ((...args: unknown[]) => void) | null;
 

src/vs/workbench/contrib/preferences/browser/media/settingsEditor2.css

@@ -344,6 +344,7 @@
 	overflow: hidden;
 	text-overflow: ellipsis;
 	display: inline-block; /* size to contents for hover to show context button */
+	padding-bottom: 2px; /* so that focus outlines wrap around nicely for indicators, especially ones with codicons */
 }
 
 .settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-modified-indicator {
@@ -368,7 +369,7 @@
 	bottom: 23px;
 }
 
-.settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-title > .misc-label {
+.settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-title > .setting-indicators-container {
 	font-style: italic;
 }
 
@@ -379,8 +380,8 @@
 	opacity: 0.9;
 }
 
-.settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-title > .misc-label .setting-indicator:hover {
-	text-decoration: underline;
+.settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-title > .setting-indicators-container .setting-indicator {
+	padding-bottom: 2px;
 }
 
 .settings-editor > .settings-body .settings-tree-container .setting-item-contents .setting-item-title .codicon {