xusheng added support for swbreak/hwbreak a month ago, and no special
support was needed in ProcessGDBRemote when they're received because
lldb already marks a thread as having hit a breakpoint when it stops at
a breakpoint site. However, with changes I am working on, we need to
know the real stop reason a thread stopped or the breakpoint hit will
not be recognized.
This is similar to how lldb processes the "watch/rwatch/awatch" keys in
a thread stop packet -- we set the `reason` to `watchpoint`, and these
set it to `breakpoint` so we set the stop reason correctly later in
these methods.