[QuadFormAndIsom]: new fix, cleanup, additional improvements and better documentation #18608

Job	Run time
doctest (1.10, Linux, RPTU, normal-memory)	31m 26s
doctest (1.11, Linux, RPTU, normal-memory)	29m 4s
doctest (1.12-nightly, Linux, RPTU, normal-memory)	35m 7s
doctest (nightly, Linux, RPTU, normal-memory)	3m 25s
doctest (1.10, Linux, RPTU, normal-memory, depwarn=error)	30m 26s
doctest (1.10, macOS, RPTU)	18m 0s
extra-long-test	0s
test (1.6, short, Linux)	19m 50s
test (1.6, long, Linux)	17m 14s
test (1.10, short, Linux)	26m 54s
test (1.10, long, Linux)	16m 51s
test (1.11, short, Linux)	16m 5s
test (1.11, long, Linux)	14m 54s
test (1.12-nightly, short, Linux)	2h 1m 56s
test (1.12-nightly, long, Linux)	27m 16s
test (nightly, short, Linux)	2m 34s
test (nightly, long, Linux)	24s
test (1.10, short, Linux, RPTU, high-memory, depwarn=error)	23m 30s
test (1.10, long, Linux, RPTU, normal-memory, depwarn=error)	21m 19s
test (1.10, short, macOS, RPTU)	13m 58s
test (1.10, long, macOS, RPTU)	12m 20s
test (1.10, book, Linux, RPTU, normal-memory)	38m 36s
test (pre, book, Linux, RPTU, normal-memory)	2h 5m 37s
test (nightly, book, Linux, RPTU, normal-memory)	2m 3s
	10h 48m 49s

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