`fn angular_ipred`: Make safe w/ `Rav1dPictureDataComponentOffset` #801

Job	Run time
test on armv7-unknown-linux-gnueabihf	8m 52s
test on aarch64-unknown-linux-gnu	8m 35s
test on x86_64-unknown-linux-gnu	11m 32s
test on riscv64gc-unknown-linux-gnu	9m 3s
	38m 2s

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