Log lots more about notification inflation

We're debugging a bug in which an incoming call notification never
appeared, and seemed like it might've been stuck partway through the
inflation process.

We also don't have great logs at the lower levels of the inflation
process.

So, add a new log buffer (NotifInflationLog) and add logging in many
more places, making sure to cover potentially slow/hung operations well.

Bug: 290800796
Test: manual
Change-Id: I891a648748b612faae1fc732b08aa057a6cb2504