appmodel: extract AppObjectGenerator base class to its own module #1492

Job	Run time
create-source-tarball	2m 46s
create-packages / almalinux-8	5m 25s
create-packages / debian-bookworm	6m 14s
create-packages / debian-testing	6m 26s
create-packages / fedora-39	6m 42s
create-packages / ubuntu-noble	8m 59s
	36m 32s

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