UseListOrder: Fix blockaddress use-list order

`parseBitcodeFile()` uses the generic `getLazyBitcodeFile()` function as
a helper.  Since `parseBitcodeFile()` isn't actually lazy -- it calls
`MaterializeAllPermanently()` -- bypass the unnecessary call to
`materializeForwardReferencedFunctions()` by extracting out a common
helper function.  This removes the last of the use-list churn caused by
blockaddresses.

This highlights that we can't reproduce use-list order of globals and
constants when parsing lazily -- but that's necessarily out of scope.
When we're parsing lazily, we never have all the functions in memory, so
the use-lists of globals (and constants that reference globals) are
always incomplete.

This is part of PR5680.

llvm-svn: 214581