Audio engine observer fixes (#571) #785

Job	Run time
test (macos-13, 14.2, iOS Simulator,OS=17.2,name=iPhone 14 Pro)	25m 18s
test (macos-13, 14.2, iOS Simulator,OS=17.2,name=iPhone 14 Pro)	25m 18s
test (macos-13, 14.2, macOS)	4m 23s
test (macos-13, 14.2, macOS)	4m 23s
test (macos-13, 14.2, macOS,variant=Mac Catalyst)	5m 2s
test (macos-13, 14.2, macOS,variant=Mac Catalyst)	5m 2s
test (macos-14, 15.4, iOS Simulator,OS=17.5,name=iPhone 15 Pro)	4m 31s
test (macos-14, 15.4, iOS Simulator,OS=17.5,name=iPhone 15 Pro)	6m 3s
test (macos-14, 15.4, macOS)	3m 23s
test (macos-14, 15.4, macOS)	3m 23s
test (macos-14, 15.4, macOS,variant=Mac Catalyst)	3m 22s
test (macos-14, 15.4, macOS,variant=Mac Catalyst)	3m 22s
test (macos-14, 15.4, visionOS Simulator,name=Apple Vision Pro)	3m 31s
test (macos-14, 15.4, visionOS Simulator,name=Apple Vision Pro)	5m 6s
test (macos-14, 15.4, tvOS Simulator,name=Apple TV)	4m 10s
test (macos-14, 15.4, tvOS Simulator,name=Apple TV)	4m 10s
test (macos-15, 16.2, iOS Simulator,OS=18.1,name=iPhone 16 Pro)	6m 32s
test (macos-15, 16.2, iOS Simulator,OS=18.1,name=iPhone 16 Pro)	6m 32s
test (macos-15, 16.2, macOS)	3m 54s
test (macos-15, 16.2, macOS)	3m 54s
test (macos-15, 16.2, macOS,variant=Mac Catalyst)	4m 8s
test (macos-15, 16.2, macOS,variant=Mac Catalyst)	4m 8s
	2h 19m 35s

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