fix: handle paste of library content blocks correctly #21136

Job	Run time
python-3.8,django-pinned,lms-1	10m 29s
python-3.8,django-pinned,lms-2	9m 10s
python-3.8,django-pinned,lms-3	15m 50s
python-3.8,django-pinned,lms-4	18m 7s
python-3.8,django-pinned,lms-5	9m 8s
python-3.8,django-pinned,lms-6	14m 3s
python-3.8,django-pinned,openedx-1-with-lms	12m 40s
python-3.8,django-pinned,openedx-2-with-lms	13m 30s
python-3.8,django-pinned,openedx-1-with-cms	7m 26s
python-3.8,django-pinned,openedx-2-with-cms	4m 24s
python-3.8,django-pinned,cms-1	2m 43s
python-3.8,django-pinned,cms-2	15m 14s
python-3.8,django-pinned,common-with-lms	8m 27s
python-3.8,django-pinned,common-with-cms	3m 55s
python-3.8,django-pinned,xmodule-with-lms	5m 0s
python-3.8,django-pinned,xmodule-with-cms	4m 59s
python-3.8,django-4.2,lms-1	10m 30s
python-3.8,django-4.2,lms-2	8m 56s
python-3.8,django-4.2,lms-3	15m 54s
python-3.8,django-4.2,lms-4	18m 59s
python-3.8,django-4.2,lms-5	9m 10s
python-3.8,django-4.2,lms-6	13m 53s
python-3.8,django-4.2,openedx-1-with-lms	13m 1s
python-3.8,django-4.2,openedx-2-with-lms	14m 15s
python-3.8,django-4.2,openedx-1-with-cms	7m 28s
python-3.8,django-4.2,openedx-2-with-cms	4m 25s
python-3.8,django-4.2,cms-1	2m 48s
python-3.8,django-4.2,cms-2	15m 50s
python-3.8,django-4.2,common-with-lms	8m 42s
python-3.8,django-4.2,common-with-cms	4m 9s
python-3.8,django-4.2,xmodule-with-lms	5m 6s
python-3.8,django-4.2,xmodule-with-cms	5m 14s
compile-warnings-report	10s
Unit tests successful	7s
coverage (3.8)	1m 48s
	5h 15m 30s

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