[XRay][compiler-rt] Add PID field to llvm-xray tool and add PID metadata record entry...

[XRay][compiler-rt] Add PID field to llvm-xray tool and add PID metadata record entry in FDR mode

Summary:
llvm-xray changes:
- account-mode - process-id  {...} shows after thread-id
- convert-mode - process {...} shows after thread
- parses FDR and basic mode pid entries
- Checks version number for FDR log parsing.

Basic logging changes:
- Update header version from 2 -> 3

FDR logging changes:
- Update header version from 2 -> 3
- in writeBufferPreamble, there is an additional PID Metadata record (after thread id record and tsc record)

Test cases changes:
- fdr-mode.cc, fdr-single-thread.cc, fdr-thread-order.cc modified to catch process id output in the log.

Reviewers: dberris

Reviewed By: dberris

Subscribers: hiraditya, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D49153

llvm-svn: 336974