Do not trigger "HotkeyPress" events when releasing a key.

Follows rP24675.
Because only the most specific hotkeys can be active at any time, releasing a key may require re-activating less specific hotkeys.
There were two issues with this behaviour:

• It was buggy, as it only checked one active key, when any still active key can trigger hotkeys.
• "HotkeyPress" and "HotkeyDown" events where sent, as if the hotkey was pressed, which was unexpected for most code/users (it is unusual to have a "Press" event on key release).

This fixes these issues by "silently" re-triggering the hotkeys in such a case. It also makes it easier for JS code to use "hotkeyPress" instead of "hotkeyDown" for non-continuous behaviour.

Accepted By: nani

Fixes #6123
Refs #6064 (fixes the problem, but not the code weirdness)

Differential Revision: https://code.wildfiregames.com/D3766