Fix debugserver's qProcessInfo reporting of maccatalyst binaries

This patch is similar in spirit to https://reviews.llvm.org/D84480,
but does the maccatalyst/macosx disambiguation. I also took the
opportunity to factor out the gdb-remote packet log scanning used by
several testcases into lldbutil functions.

rdar://problem/66059257

Differential Revision: https://reviews.llvm.org/D84576