Account for unreleased frames when predicting resampler needs

Other changes related to resampling:
 - improve logs
 - use correct form of assert
 - don't round up max usable circular buffer sizes to power of 2;
   this gives more predictable results
 - add some FIXMEs

Bug: 13133176
Change-Id: I8d3c90eed4eb0c0c1fbac3c864e179a2806c2301