[trace][intel-pt] Implement trace start and trace stop

This implements the interactive trace start and stop methods.

This diff ended up being much larger than I anticipated because, by doing it, I found that I had implemented in the beginning many things in a non optimal way. In any case, the code is much better now.

There's a lot of boilerplate code due to the gdb-remote protocol, but the main changes are:

- New tracing packets: jLLDBTraceStop, jLLDBTraceStart, jLLDBTraceGetBinaryData. The gdb-remote packet definitions are quite comprehensive.
- Implementation of the "process trace start|stop" and "thread trace start|stop" commands.
- Implementaiton of an API in Trace.h to interact with live traces.
- Created an IntelPTDecoder for live threads, that use the debugger's stop id as checkpoint for its internal cache.
- Added a functionality to stop the process in case "process tracing" is enabled and a new thread can't traced.
- Added tests

I have some ideas to unify the code paths for post mortem and live threads, but I'll do that in another diff.

Differential Revision: https://reviews.llvm.org/D91679

lldb/source/Utility/StringExtractorGDBRemote.cpp

@@ -303,18 +303,17 @@ StringExtractorGDBRemote::GetServerPacketType() const {
       return eServerPacketType_jSignalsInfo;
     if (PACKET_MATCHES("jThreadsInfo"))
       return eServerPacketType_jThreadsInfo;
-    if (PACKET_STARTS_WITH("jTraceBufferRead:"))
-      return eServerPacketType_jTraceBufferRead;
-    if (PACKET_STARTS_WITH("jTraceConfigRead:"))
-      return eServerPacketType_jTraceConfigRead;
-    if (PACKET_STARTS_WITH("jTraceMetaRead:"))
-      return eServerPacketType_jTraceMetaRead;
-    if (PACKET_STARTS_WITH("jTraceStart:"))
-      return eServerPacketType_jTraceStart;
-    if (PACKET_STARTS_WITH("jTraceStop:"))
-      return eServerPacketType_jTraceStop;
-    if (PACKET_MATCHES("jLLDBTraceSupportedType"))
-      return eServerPacketType_jLLDBTraceSupportedType;
+
+    if (PACKET_MATCHES("jLLDBTraceSupported"))
+      return eServerPacketType_jLLDBTraceSupported;
+    if (PACKET_STARTS_WITH("jLLDBTraceStop:"))
+      return eServerPacketType_jLLDBTraceStop;
+    if (PACKET_STARTS_WITH("jLLDBTraceStart:"))
+      return eServerPacketType_jLLDBTraceStart;
+    if (PACKET_STARTS_WITH("jLLDBTraceGetState:"))
+      return eServerPacketType_jLLDBTraceGetState;
+    if (PACKET_STARTS_WITH("jLLDBTraceGetBinaryData:"))
+      return eServerPacketType_jLLDBTraceGetBinaryData;
     break;
 
   case 'v':