[XRay] Stable sort XRayRecord to remove non-deterministic ordering

Summary:
This fixes failure in tools/llvm-xray/X86/graph-zero-latency-calls.yaml
uncovered by D39245.

Reviewers: dberris

Reviewed By: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D39943

llvm-svn: 318163