[Backport release-3_40] [vector layer] Fix newly-added features in the edit buffer prior to adding a new attribute will not save the new attribute's values #36648

Job	Run time
build (24.04, 5, true, OFF, ON, ON, ON, ON, OFF, OFF, OFF, OFF, ON, false)	1h 50m 16s
build (39, 6, true, ON, OFF, ON, ON, OFF, OFF, ON, ON, ON, OFF, false)	3h 5m 3s
clang-tidy (24.04, 5)	5m 57s
Run tests (5, ALL_BUT_PROVIDERS)	28m 54s
Run tests (5, POSTGRES)	6m 28s
Run tests (5, HANA)	5m 31s
Run tests (6, ALL_BUT_PROVIDERS)	36m 32s
Run tests (5, ORACLE, 24.04, binary-for-oracle)	6m 17s
	6h 24m 58s

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