[lldb] Add support for recognizing swift mangled names
Apple maintains a downstream fork of lldb in order to support swift
debugging. Much of that support is isolated to its own plugins, but some
of it is exposed in more generic code. I would like to take some of
the swift support we have downstream and move it upstream to llvm.org in
an effort to 1) reduce downstream maintenance burden, and 2) work
towards solidifying the process of adding new language support to lldb.
Differential Revision: https://reviews.llvm.org/
D158470