simpleperf: Report lost samples in kernel space and user space

Currently we only report total lost samples by default. It's not
clear where the samples are lost and we should increase the size of
which buffer.

To improve it:
1) Calculate records lost in kernel space in RecordStat, instead of
   in RecordCmd.
2) Report lost samples in kernel space and user space separately.
3) Give different warnings for samples lost in kernel space and
   samples lost in user space.

Bug: 276029326
Test: run simpleperf_unit_test
Change-Id: I312175f9b59312f3606f03c0668b9b84e70df0c3
4 files changed