Camera: Add details about default output YUV encoding

Make it clear that YUV_420_8888 buffers from camera
1) Are using JFIF YUV<->RGB transforms
2) Should be interpreted as sRGB after conversion to sRGB

Also fix some broken doc links in the camera package.

Test: m offline-sdk-docs
Bug: 290382236

Change-Id: Iaf18df8371e596a498d14c33abd495a1d367a311