refactor: update box-shadow styles across various components to use new shadow variables

- Replaced hardcoded box-shadow values with new CSS variables for consistency and improved theming.
- Updated styles in postEditWidget, findOptionsWidget, findWidget, floatingMenu, hover, parameterHints, peekViewWidget, renameWidget, stickyScroll, suggest, actionWidget, hover, quickInput, agentFeedback components, and more.
- Introduced new shadow variables: --vscode-shadow-sm, --vscode-shadow-md, --vscode-shadow-lg, --vscode-shadow-xl, and --vscode-shadow-hover for better control over shadow effects.

Co-authored-by: Copilot <copilot@github.com>

src/vs/base/browser/ui/dialog/dialog.css

@@ -31,6 +31,7 @@
 	padding: 10px;
 	transform: translate3d(0px, 0px, 0px);
 	border-radius: var(--vscode-cornerRadius-large);
+	box-shadow: var(--vscode-shadow-xl);
 }
 
 .monaco-dialog-box.align-vertical {

src/vs/base/browser/ui/dropdown/dropdown.css

@@ -22,6 +22,7 @@
 
 .monaco-dropdown .dropdown-menu {
 	border-radius: var(--vscode-cornerRadius-large);
+	box-shadow: var(--vscode-shadow-lg);
 }
 
 .monaco-dropdown-with-primary {

src/vs/base/browser/ui/menu/menu.ts

@@ -322,13 +322,11 @@ export class Menu extends ActionBar {
 		const bgColor = style.backgroundColor ?? '';
 		const border = style.borderColor ? `1px solid ${style.borderColor}` : '';
 		const borderRadius = 'var(--vscode-cornerRadius-large)';
-		const shadow = style.shadowColor ? `0 2px 8px ${style.shadowColor}` : '';
 
 		scrollElement.style.outline = border;
 		scrollElement.style.borderRadius = borderRadius;
 		scrollElement.style.color = fgColor;
 		scrollElement.style.backgroundColor = bgColor;
-		scrollElement.style.boxShadow = shadow;
 	}
 
 	override getContainer(): HTMLElement {
@@ -1241,6 +1239,7 @@ ${formatRule(Codicon.menuSubmenu)}
 	border: none;
 	animation: fadeIn 0.083s linear;
 	-webkit-app-region: no-drag;
+	box-shadow: var(--vscode-shadow-lg);
 }
 
 .context-view.monaco-menu-container :focus,

src/vs/base/browser/ui/selectBox/selectBoxCustom.css

@@ -7,7 +7,7 @@
 	display: none;
 	box-sizing: border-box;
 	border-radius: var(--vscode-cornerRadius-large);
-	box-shadow: 0 2px 8px var(--vscode-widget-shadow);
+	box-shadow: var(--vscode-shadow-lg);
 }
 
 .monaco-select-box-dropdown-container > .select-box-details-pane > .select-box-description-markdown * {