[MRTK3] Port Enabled SeeItSayIt Labels (#11466)

- Adds a SeeItSayItLabelEnabler script which enables See-It Say-It labels at runtime, if voice commands are enabled for a button and the speech and input packages are installed.

- Adds anims to uxcomponents and uxcomponents.noncanvas, and adds a StateVisualizer component to canvas and non-canvas See-It Say-It label prefabs, to show See-It Say-It label on active hover.

- Updates the canvas and non-canvas button prefabs (Empty Button and Pressable Button_128x32mm_TextOnly) to add See-It Say-It Labels (disabled by default) and the SeeItSayItLabelEnabler. 

- Updates the SeeItSayIt Example scene to use the SeeItSayItLabelEnabler component to enable labels at runtime. 

- Adds unit tests for canvas and non-canvas label prefabs, as well as SeeItSayItLabelEnabler script.

- Adds null checks to StateVisualizer.