enable parentless frame for tooltip

[mikeandmore]

Currently, the document tooltip frame is a child frame, which is constrained to the main Emacs window. If the content width is too wide and company-box-doc-no-wrap is nil, then company-box will wrap the child frame. This makes the child frame extremely narrow when there is not enough space left inside the Emacs window. However, with company-box-doc-no-wrap being t, the frame will be cut off in half, hiding half of the content even when there is plenty of space outside of the Emacs window.

This PR creates the document tooltip as a parentless frame (parent-frame . nil) when company-box-doc-no-wrap is t. When the content is too wide for the Emacs window, the frame will popup outside the Emacs window.