More packet reduction when debugging with GDB server.

- Avoid sending the qfThreadInfo, qsThreadInfo packets if we have a stop reply packet with the threads already (save 2 round trip packets)
- Include the qname, qserial and qkind in the JSON info
- Report the qname, qserial and qkind to the thread so it can cache it to avoid many packets on MacOSX and iOS
- Don't clear all discoverable settings when we exec, just the ones we need to saves 1-5 packets for each exec.

llvm-svn: 240988