[3.13] gh-120041: Do not use append_to_screen when completions are visible (GH-120042) (#120051)

* gh-120041: Do not use append_to_screen when completions are visible (GH-120042)
(cherry picked from commit 8fc7653766b106bdbc4ff6154e0020aea4ab15e6)

* gh-120041: Refactor check for visible completion menu in completing_reader (GH-120055)
(cherry picked from commit bf8e5e53d0c359a1f9c285d855e7a5e9b6d91375)
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Co-authored-by: Lysandros Nikolaou <lisandrosnik@gmail.com>