[codeview] Move StreamInterface and StreamReader to libcodeview.

[codeview] Move StreamInterface and StreamReader to libcodeview.

We have need to reuse this functionality, including making
additional generic stream types that are smarter about how and
when they copy memory versus referencing the original memory.
So all of these structures belong in the common library
rather than being pdb specific.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270751 91177308-0d34-0410-b5e6-96231b3b80d8