Revert r301697 "[IR] Make add/remove Attributes use AttrBuilder instead of AttributeList"

This broke the Clang build. (Clang-side patch missing?)

Original commit message:

> [IR] Make add/remove Attributes use AttrBuilder instead of
> AttributeList
>
> This change cleans up call sites and avoids creating temporary
> AttributeList objects.
>
> NFC

llvm-svn: 301712