tmt: Add tests for etc merge conflict #266

Job	Run time
publish-images (fedora-43, composefs-sealeduki-sdboot)	34m 40s
publish-images (fedora-44, ostree)	31m 11s
publish-images (centos-9, ostree)	31m 40s
publish-images (fedora-45, ostree)	33m 38s
publish-images (fedora-43, ostree)	35m 1s
publish-images (fedora-45, composefs-sealeduki-sdboot)	36m 22s
publish-images (fedora-44, composefs-sealeduki-sdboot)	34m 4s
publish-images (centos-10, ostree)	35m 16s
publish-images (centos-10, composefs-sealeduki-sdboot)	33m 37s
	5h 5m 29s

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