[XRay] ARM 32-bit no-Thumb support in LLVM

[XRay] ARM 32-bit no-Thumb support in LLVM

This is a port of XRay to ARM 32-bit, without Thumb support yet. The XRay instrumentation support is moving up to AsmPrinter.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

https://reviews.llvm.org/D23932 (Clang test)
https://reviews.llvm.org/D23933 (compiler-rt)

Differential Revision: https://reviews.llvm.org/D23931

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281878 91177308-0d34-0410-b5e6-96231b3b80d8