Rewrite lilypond-invoke-editor in Python

lilypond-invoke-editor is currently the only script written in Scheme. If it was (re)written in Python, all (distributed) scripts would use the same scripting language and we could stop including a stand-alone guile executable.

added Scripts label

(All of this assuming that we want to continue offering lilypond-invoke-editor for power users.)

mentioned in issue #2279 (closed)

assigned to @hahnjo

mentioned in merge request !1229 (merged)

closed with commit 75794436

changed milestone to %2.23.10

mentioned in commit 75794436