Spannable-Core: Add SetSpannedText API

Spannable-Core: Add SetSpannedText API

  Copy text from Spanned-Text into TextController and apply styles on it.

  void SetSpannedText(TextController textController, const Spanned& spannedText);

  TextController: TextLabel, TextEditor or TextField

  This patch should be preceded by the patch below:
  https://review.tizen.org/gerrit/c/platform/core/uifw/dali-toolkit/+/282806

//Example:

    Dali::Toolkit::Text::SpannableString ss = Dali::Toolkit::Text::SpannableString::New("Hello مرحبا");

    auto isAddedBlue = ss.AttachSpan(
      Dali::Toolkit::Text::ForegroundColorSpan::New(Color::BLUE),
      Dali::Toolkit::Text::Range::New(2u, 4u));

    Dali::Toolkit::Text::SetSpannedText(textLabel, ss);

Change-Id: I03202eb27376d78403050a284a1448f01c4ac120