LiveEffect demo feature request: AEC button

[chrbsg]

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The LiveEffect demo suffers from echo feedback when using phone microphone and speakers. Would it be possible to add a UI button to enable AEC? (such a demo was also previously requested by others in #85 ). And also, if possible, a text widget to show whether AEC is hardware or software.

(The motivation for this is that it is not clear how to query and enable hardware AEC from Oboe - suggestion seems to be to use the Java API AcousticEchoCanceler which implies that this can't be done from within C++, and it's not clear whether AcousticEchoCanceler requires usage of AudioRecord, which means microphone audio has to be read in Java code?)

[philburk]

It might be good to have a local AEC that can be compared with the OS AEC. Using the OS AEC causes very high latency.

[robertwu1]

Added to OboeTester. Not adding this to samples as it increases latency too much