Load radare2 plugins from the iaito plugins directory too #634

Job	Run time
acr-linux-r2git	6m 14s
acr-linux	4m 42s
acr-macos-x64	9m 48s
acr-macos-m1	3m 33s
meson (ubuntu-24.04, 3.8.x, true, default, default)	7m 58s
w64-meson	8m 52s
meson (ubuntu-22.04, 3.8.x, true, default, default)	6m 49s
meson (ubuntu-20.04, 3.8.x, true, default, default)	6m 3s
check_release	4s
release	0s
	54m 3s

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