Information on server crash lost as output channel is closed

[aeschli]

When the language server crashes 5 times, it is hard to find out what went wrong as the output channel is closed
(https://github.com/Microsoft/vscode-languageserver-node/blob/master/client/src/client.ts#L2790)

-> do not close the output channel
-> also log crash errors to the extension host console (and log)