give TextureProgressBar "indeterminate"

[FourGames]

regular progress bar has indeterminate and editor preview but not texture progress bar would be nice if it also had it could make circular loading symbols and much more with it easy

[Calinou]

• Related to Add mixed state to Checkbox (and perhaps other controls) #8241.

TextureProgressBars often have fancier designs than ProgressBars, so I'm not sure how often a built-in indeterminate property would be used. Different people will want to animate it in different ways (e.g. cycle, pingpong back and forth, various easings and speeds...). This can all already be achieved with AnimationPlayer or Tween.