fix: move BlockKey and derived_key to avoid cyclical import #21762

Job	Run time
python-3.8,django-pinned,lms-1	10m 17s
python-3.8,django-pinned,lms-2	8m 58s
python-3.8,django-pinned,lms-3	16m 3s
python-3.8,django-pinned,lms-4	18m 28s
python-3.8,django-pinned,lms-5	8m 56s
python-3.8,django-pinned,lms-6	15m 21s
python-3.8,django-pinned,openedx-1-with-lms	12m 50s
python-3.8,django-pinned,openedx-2-with-lms	14m 29s
python-3.8,django-pinned,openedx-1-with-cms	7m 8s
python-3.8,django-pinned,openedx-2-with-cms	4m 12s
python-3.8,django-pinned,cms-1	2m 40s
python-3.8,django-pinned,cms-2	15m 21s
python-3.8,django-pinned,common-with-lms	8m 59s
python-3.8,django-pinned,common-with-cms	3m 53s
python-3.8,django-pinned,xmodule-with-lms	5m 1s
python-3.8,django-pinned,xmodule-with-cms	5m 9s
python-3.8,django-4.2,lms-1	10m 36s
python-3.8,django-4.2,lms-2	9m 14s
python-3.8,django-4.2,lms-3	16m 25s
python-3.8,django-4.2,lms-4	19m 26s
python-3.8,django-4.2,lms-5	8m 59s
python-3.8,django-4.2,lms-6	15m 5s
python-3.8,django-4.2,openedx-1-with-lms	12m 45s
python-3.8,django-4.2,openedx-2-with-lms	14m 27s
python-3.8,django-4.2,openedx-1-with-cms	7m 14s
python-3.8,django-4.2,openedx-2-with-cms	4m 20s
python-3.8,django-4.2,cms-1	2m 45s
python-3.8,django-4.2,cms-2	18m 7s
python-3.8,django-4.2,common-with-lms	8m 54s
python-3.8,django-4.2,common-with-cms	4m 3s
python-3.8,django-4.2,xmodule-with-lms	5m 0s
python-3.8,django-4.2,xmodule-with-cms	5m 12s
compile-warnings-report	10s
coverage (3.8)	1m 45s
Unit tests successful	1s
	5h 22m 13s

Provide feedback