Support getDeviceIds API

[flamme]

From API 36, aaudio added AAudioStream_getDeviceIds API, which can return multiple device IDs when there are multiple devices used. For instance, for ringtone and alarm on phone with peripheral devices connected. In that case, it should be also added to oboe.

[robertwu1]

There are a couple ways we can write the oboe API for OboeStream.getDevices(). Copying the AAudio API below for reference.

/**
 * Call this function after AAudioStreamBuilder_openStream().
 * An array of size 16 should generally be large enough to fit all device identifiers.
 *
 * Available since API level 36.
 *
 * @param stream reference provided by AAudioStreamBuilder_openStream().
 * @param ids reference to an array of ids.
 * @params numIds size allocated to the array of ids.
 *         The input should be the size of the ids array.
 *         The output will be the actual number of device ids.
 * @return {@link #AAUDIO_OK} or an error code.
 *         If numIds is null, return {@link #AAUDIO_ERROR_ILLEGAL_ARGUMENT}.
 *         If numIds is smaller than the number of device ids, return
 *         {@link #AAUDIO_ERROR_OUT_OF_RANGE}. The value of numIds will still be updated.
 *         Otherwise, if ids is null, return {@link #AAUDIO_ERROR_ILLEGAL_ARGUMENT}.
 */
AAUDIO_API aaudio_result_t AAudioStream_getDeviceIds(AAudioStream* _Nonnull stream,
        int32_t* _Nullable ids, int32_t* _Nullable numIds) __INTRODUCED_IN(36);

1. We can use the exact same API in oboe with ids and numIds being the two parameters for an Oboe. It's look like oboe::Result getDeviceIds(int32_t* ids, int32_t* numIds)
2. By querying AAudioStream_getDeviceIds with an empty ids array, we can get numIds. This way, we can call AAudioStream_getDeviceIds again with the arrays with a fixed size and it should just work. We can pack this into an std::vector. The function can look like vector<int32_t> getDeviceIds().
3. We can do something similar like option 2 but pass by parameter. The function can be void getDeviceIds(vector<int32_t>& deviceIds).

I prefer option 2. @flamme @philburk what do you guys think?

[flamme]

Option 2 looks good to me. One thing to be noted is that the device ids may be changed after querying getDeviceIds for the first time even though at this case the stream is connected.

[robertwu1]

Yea, if the size changes after querying it again, we can keep trying until the size is consistent