[IR] Straighten out bundle overload of IRBuilder::CreateCall

IRBuilder has two ways of putting bundle operands on calls: the default
operand bundle, and an overload of CreateCall that takes an operand
bundle list.

Previously, this overload used a default argument of None. This made it
impossible to distinguish between the case were the caller doesn't care
about bundles, and the case where the caller explicitly wants no
bundles. We behaved as if they wanted the latter behavior rather than
the former, which led to problems with simplifylibcalls and WinEH.

This change fixes it by making the parameter non-optional, so we can
distinguish these two cases.

llvm-svn: 261258