[NFC] Add new setDebugLocFromInst that uses the class Builder by default

In lots of places we were calling setDebugLocFromInst and passing
in the same Builder member variable found in InnerLoopVectorizer.
I personally found this confusing so I've changed the interface
to take an Optional<IRBuilder<> *> and we can now pass in None
when we want to use the class member variable.

Differential Revision: https://reviews.llvm.org/D105100