BlockListStore doesn't need to keep the buffer after the block-list is
parsed. Don't share the same source manager as the compilation so it
doesn't need to make sure the buffer is valid during the entire duration
of the compilation.
rdar://137448231
Make sure block-list file is read through VFS so CASFS can be used to
read the configuration to ensure sound caching, and also the path of the
blocklist can be canonicalized via path remapping.
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
