[opaque pointer type] Provide a convenience for IRBuilder::CreateCall that accepts...

[opaque pointer type] Provide a convenience for IRBuilder::CreateCall that accepts a Function without needing to take an explicit callee Type

The common case is a direct call, so don't make all those users have to
explicitly pass the result of llvm::Function::getFunctionType.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237627 91177308-0d34-0410-b5e6-96231b3b80d8