fix(ui5-menu): restore focus to the opener

[unazko]

• The focus is restored over the opener element after root menu close.
• Redundant icon dependency is removed from the menu.
• Escape keyboard key press closes all dialogs on mobile device.
• Sub-menu could not be opened from a disabled ui5-menu-item.
• The leftover start-section property usage is replaced with the ui5-menu-separator component usage.

Fixes: #9317

[unazko]

The prevent-focus-restore attribute is now removed from the menu template as a better approach for restoring the focus to the opener button pointed out by @TeodorTaushanov.

[nnaydenow]

Test looks good to me but I haven’t review the rest of PR.

[tsanislavgatev]

Merge main into your branch to get the change that makes the tests stable.

[nnaydenow]

Test is failing because following code doesn't work and the focus is not restored to the button when the menu is closed.

	<ui5-button id="test">Open Menu</ui5-button>
	<ui5-menu>
		<ui5-menu-item text="New File">
		</ui5-menu-item>
	</ui5-menu>
	<script>
			const button = document.querySelector("#test")

			button.addEventListener("click", (e) => {
				const menu = document.querySelector("[ui5-menu]")
				menu.open = true;
				menu.opener = e.target;
			})
	</script>

Tested manually with latest and the fix does not work as expected in the github issue.

[tsanislavgatev]

After discussion and additional test we've came to the conclusion that the latest version works as expected and described in the issue.