[Backport release-3_40] Optimise conversion of QgsAttributes to Python objects #37628

Job	Run time
build (24.04, 5, true, OFF, ON, ON, ON, ON, OFF, OFF, OFF, OFF, ON, false)	29m 12s
build (39, 6, true, ON, OFF, ON, ON, OFF, OFF, ON, ON, ON, OFF, false)	36m 36s
clang-tidy (24.04, 5)	9m 18s
Run tests (5, ALL_BUT_PROVIDERS)	29m 53s
Run tests (5, POSTGRES)	7m 44s
Run tests (5, HANA)	7m 22s
Run tests (6, ALL_BUT_PROVIDERS)	38m 16s
Run tests (5, ORACLE, 24.04, binary-for-oracle)	7m 33s
	2h 45m 54s

Provide feedback