InternalScopedString uses InternalMmapVector internally
so it can be resized dynamically as needed.
Reviewed By: eugenis
Differential Revision: https://reviews.llvm.org/D98751
Right now, when you have an invalid memory address, asan would just crash and does not offer much useful info.
This patch attempted to give a bit more detail on the access.
Differential Revision: https://reviews.llvm.org/D98280