[WindowsResource] Remove use of global variables in WindowsResourceParser

Instead of updating a global variable counter for the next index of
strings and data blobs, pass along a reference to actual data/string
vectors and let the TreeNode insertion methods add their data/strings to
the vectors when a new entry is needed.

Additionally, if the resource tree had duplicates, that were ignored
with -force:multipleres in lld, we no longer store all versions of the
duplicated resource data, now we only keep the one that actually ends
up referenced.

Differential Revision: https://reviews.llvm.org/D66823

llvm-svn: 370435