Add `val_modalities` #10905

Job	Run time
flambda2_runtime5	9m 8s
flambda2_dev	7m 24s
flambda2_dev_runtime5	8m 6s
flambda2_debug_runtime5	12m 5s
flambda2_debug_runtime	11m 4s
flambda2_o3	9m 42s
flambda2_o3_heap	8m 25s
flambda2_o3_advanced_meet_frame_pointers_runtime5	9m 55s
flambda2_o3_advanced_meet_frame_pointers_runtime5_debug	11m 10s
flambda2_frame_pointers_oclassic	8m 45s
flambda2_macos	25m 4s
irc	8m 57s
irc_frame_pointers	9m 17s
ls	8m 42s
gi	8m 54s
	2h 36m 38s

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