Revert "[Support] Add raw_ostream_iterator: ostream_iterator for raw_ostream"

This reverts commit 7479a2e0.

This commit causes compile errors on clang-x64-windows-msvc, so I'm
reverting the patch for now.

For reference, the error in question is:

```
error C2280: 'llvm::raw_ostream_iterator<char,char>
&llvm::raw_ostream_iterator<char,char>::operator =(const
llvm::raw_ostream_iterator<char,char> &)': attempting to reference a deleted
function

note: compiler has generated 'llvm::raw_ostream_iterator<char,char>::operator ='
here

note: 'llvm::raw_ostream_iterator<char,char>
&llvm::raw_ostream_iterator<char,char>::operator =(const
llvm::raw_ostream_iterator<char,char> &)': function was implicitly deleted
because 'llvm::raw_ostream_iterator<char,char>' has a data member
'llvm::raw_ostream_iterator<char,char>::OutStream' of reference type
```