Simpleperf: better support for per thread comm.

1. Move ProcessEntry to ThreadEntry, and add thread_comm in SampleEntry.
2. Add support of ForkRecord and Mmap2Record.
3. Dump ForkRecord for each thread in record command.
4. Add sort key 'tid' in report command, and change default keys.

Bug: 19483574
Change-Id: Iacc690637154aeb7b6f85373730beb50d638ce86
10 files changed