feat!: Drop the block_structure.storage_backing_for_cache WaffleSwitch #31154

Job	Run time
collect-and-verify	4m 17s
lms-1(py=3.11,dj=pinned,mongo=7.0)	9m 58s
lms-2(py=3.11,dj=pinned,mongo=7.0)	11m 48s
lms-3(py=3.11,dj=pinned,mongo=7.0)	14m 56s
lms-4(py=3.11,dj=pinned,mongo=7.0)	20m 17s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 32s
lms-6(py=3.11,dj=pinned,mongo=7.0)	15m 15s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 14s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	15m 2s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 53s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 22s
cms-1(py=3.11,dj=pinned,mongo=7.0)	4m 52s
cms-2(py=3.11,dj=pinned,mongo=7.0)	13m 12s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	10m 31s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 50s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 45s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	9m 20s
Unit tests successful	2s
compile-warnings-report	11s
coverage (3.11)	1m 42s
merge-artifacts	6s
	3h 6m 5s

Provide feedback