fix: resolve caption state handling and CSS issues

[idebenone]

Problem

• The caption feature in the Image Tool wasn't properly reflecting the correct state when preloaded data contained a caption.
  
• The tune state for the caption wasn't consistent.
  
• CSS styling for visually showing/hiding caption field was altering the inline-toolbar position.
  
• select an image button was hidden in uploading state causing a bad UX if user doesn't select any file.
  

Solution

• Corrected the logic to properly handle the caption state when loading pre-existing data.

    if (data.caption) {
      this.setTune('caption', true);
    }

• Introduced an utility function which determines the tune state directly reading the CSS rather than depending on this._data values.
• Instead of depending on display property, relying on visibility fixed the problem.
• Removed button's styling display: none during uploading state.

[orbachar]

Hi thanks for the fix, but now the caption input is hidden by default

users of our app got confused

is it a bug or by design?