error handling: report MI errors via vscode error notifications

[GitMensch]

Seen today when trying to just do a quick debugging session and reporting to #24 but is a general topic:

There are sometimes MI error reportings, example:

(gdb)
GDB -> App: {"token":6,"outOfBandRecord":[],"resultRecords":{"resultClass":"done","results":[]}}
addBreakPoint
stdin: 7-exec-run
stdout: =thread-group-started,id="i1",pid="26564"
GDB -> App: {"outOfBandRecord":[{"isStream":false,"type":"notify","asyncClass":"thread-group-started","output":[["id","i1"],["pid","26564"]]}]}
stdout: =thread-created,id="1",group-id="i1"
GDB -> App: {"outOfBandRecord":[{"isStream":false,"type":"notify","asyncClass":"thread-created","output":[["id","1"],["group-id","i1"]]}]}
stdout: ~"[New Thread 26564.0x34a8]\n"
GDB -> App: {"outOfBandRecord":[{"isStream":true,"type":"console","content":"[New Thread 26564.0x34a8]\n"}]}
[New Thread 26564.0x34a8]
stdout: 7^running
*running,thread-id="all"
(gdb)
GDB -> App: {"token":7,"outOfBandRecord":[],"resultRecords":{"resultClass":"running","results":[]}}
GDB -> App: {"outOfBandRecord":[{"isStream":false,"type":"exec","asyncClass":"running","output":[["thread-id","all"]]}]}
stdout: =thread-exited,id="1",group-id="i1"
GDB -> App: {"outOfBandRecord":[{"isStream":false,"type":"notify","asyncClass":"thread-exited","output":[["id","1"],["group-id","i1"]]}]}
stdout: =thread-group-exited,id="i1"
7^error,msg="During startup program exited with code 0xc0000135."
(gdb)
GDB -> App: {"outOfBandRecord":[{"isStream":false,"type":"notify","asyncClass":"thread-group-exited","output":[["id","i1"]]}]}
GDB -> App: {"token":7,"outOfBandRecord":[],"resultRecords":{"resultClass":"error","results":[["msg","During startup program exited with code 0xc0000135."]]}}
During startup program exited with code 0xc0000135.
getThreads
stdin: 8-thread-info
stdout: 8^done,threads=[]
(gdb)
GDB -> App: {"token":8,"outOfBandRecord":[],"resultRecords":{"resultClass":"done","results":[["threads",[]]]}}

Expectation: in case of resultClass":"error": "do something" with theresults, in case of msg being set (without checking I guess it is always set) then execute window.showErrorMessage(results.msg);