Use gjs's Smart GTypeName computation
Make gjs to compute the GType name for registered GObject-derived classes using the file basename and the first directory name, so that we can avoid name clashing, and ensure that no extension will break the shell by registering a name that is already used (by the shell or by any other extension).
This requires gjs@8d50e2b4 [1] that will be part of release 3.35.2.
[1] gjs!337 (merged)
Not being released yet in gjs, I can't change the dependency on meson.build file, we could temporarily add a runtime check, but probably not worth since we're in the dev cycle already.