Rework how lldb warngs about kexts that failed to load in a

Rework how lldb warngs about kexts that failed to load in a
darwin kernel debug session.

Originally, the kext name & uuid were emitted in the middle of the
kext-loading period's.  Last week I decided to try not printing
any details about kexts that failed to load, only printing a summary
of how many failed to load.

This time I'm print different progress characters depending on whether
the kext loaded or not ("-" for not), then at the end I will print a
summary of how many kexts failed to load and a sorted list of the
kexts with the bundle ID and the uuid.  It's a lot more readable.

<rdar://problem/48654569>

llvm-svn: 355958