When testing my SBProgress DAP PR (#123826), I noticed Progress update messages aren't sent over DAP. This patch adds the lldb progress event's message to the body when sent over DAP. Before  Now  Tested with my [progress tester command](https://gist.github.com/Jlalond/48d85e75a91f7a137e3142e6a13d0947), testing 10 events 5 seconds apart 1-10