[Coverage] Provide a stable order for getInstantiationGroups
[Coverage] Provide a stable order for getInstantiationGroups

Differential Revision: https://reviews.llvm.org/D39257

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@316523 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 40fea70ae766fe26b43bba9ac89b41a71c6d558d)

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm