fix(menu): no focus on first item if no selected items

[Rajdeepc]

Description

Motivation and context

Fixes the focus behavior to only set focus on selected items when the overlay is opened via click, as requested.

Related issue(s)

• fixes SWC-1020
• [Bug]: First sp-menu-item is still focused when opened with click #5610

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[nikkimk]

First, you should reference the original GitHub issue (#5610) on the PR description.

Second, from that very ticket: 

This is likely due to the modal overlay's focus trapping behavior (focusing on the first focusable element).

Menu should ALWAYS focus on an item when it receives focus. Not all overlays should autofocus.