fix(ui5-split-button): fire click event when focused with shift + tab

[hinzzx]

Main Problem

There was an issue, where if the ui5-split-button was to be focused by using Shift + Tab combination, the click event wasn't firing, after the first time a default action was executed (pressed Enter or Space).

The reason behind this, was a flag called _shiftOrEscapePressed.
Since the component has a handler for focus-in event which was just early returning if the component matches the :focus-within CSS selector, which was causing the flag to NOT reset. Therefore the component wasn't firing click event, due to the condition:

_fireClick(e?: Event) {
   e?.stopPropagation();
   if (!this._shiftOrEscapePressed) {
      this.fireDecoratorEvent("click");
   }
   this._shiftOrEscapePressed = false;
}

Solutions

• We solved few issues, by introducing a new flag called _shiftOrEscapePressedDuringSpace, which handles the cases only when Shift or Escape keys are pressed simultaneously with the Space Bar.
• Deleted an unused forgotten flag;
• Handled an issue where the arrow button was being 'frozen' if simultaneously pressing ArrowUp/Down keys and Tab/Shift + Tab.
• Shift/Escape keys now correctly prevent events from firing;
• Fixed a bug where arrow-button fired click AND arrow-click events.

Note: Test will be written in a separate change when migrating the SplitButton.spec.js file to a SplitButton.cy.tsx

Fixes: #11115

[Copilot]

Pull Request Overview

This PR fixes an issue where the ui5-split-button failed to fire the click event when focused with Shift + Tab and refines the key event handling logic.

• Removed the onFocusIn handler from the button template.
• Renamed and replaced the flag handling (using _shiftOrEscapePressedDuringSpace instead of _shiftOrEscapePressed) to address conflicts with combined key presses.
• Refactored key event handlers to reset UI states and correctly manage default actions.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/main/src/SplitButtonTemplate.tsx	Removed the onFocusIn attribute from the button template to prevent premature state resetting.
packages/main/src/SplitButton.ts	Renamed the flag and refactored key event handling logic for correct click event firing behavior.

[didip1000]

I suggest combining this statement and the one below into a variable like "shouldToggleOffActiveButton" and then if (should ...): this._buttonActive = false to avoid the duplicate code

[tsanislavgatev]

I don't really like the idea of always having flags to follow the states. Can we use checks for modifier keys? Can we try this? If not we can fallback to this solution, but let's explore using checks in the events for key modifiers. An example can be seein in Keys.js in the method isSpaceShift.