Update aaudio metrics.

1) Remove caller name as it is not required.
2) Use 0 as the first value for unknown value, which is the default
   value.
3) Add content type and sample rate.

Bug: 183154959
Test: adb shell dumpsys media.metrics
Change-Id: I710101ed0b68fc8f635346e6b480a4d72d83be55