[XRay] Add a test for function id encoding/decoding (NFC)
[XRay] Add a test for function id encoding/decoding (NFC)

Increase test coverage for function enter/exit encoding/decoding.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@346477 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt