Adds a telemetry event to record errors generated by tsserver.

Note that this records all error-responses from tsserver except cancellations. This includes:

• errors thrown while processing a request (we parse out the message and stack in this case)
• requests that do not generate a response when one is expected
• unrecognized JSON commands the server is asked to execute

These events should not be raised often, but part of the reason we would like to get information about these is that we really don't know, since tsserver swallows the errors and continues to run.