[COFF, ARM64] Add support for Windows ARM64 COFF format

Summary:
This is the llvm part of the initial implementation to support Windows ARM64 COFF format.
I will gradually add more functionality in subsequent patches.

Reviewers: ruiu, rnk, t.p.northover, compnerd

Reviewed By: ruiu, compnerd

Subscribers: aemerson, mgorny, javed.absar, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D34705

llvm-svn: 306490