internal/lsp: add additional information when logging errors

Fixes golang/go#33499

This logs additional information compatible with `golang.org/x/xerrors` like the frames.

Change-Id: If25c3979cf294dbe55b0e3d9d999b24c1ff8900d
GitHub-Last-Rev: 210fa40
GitHub-Pull-Request: #144
Reviewed-on: https://go-review.googlesource.com/c/tools/+/189344
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/telemetry/event.go

@@ -22,7 +22,11 @@ func (e Event) Format(f fmt.State, r rune) {
 	}
 	fmt.Fprint(f, e.Message)
 	if e.Error != nil {
-		fmt.Fprintf(f, ": %v", e.Error)
+		if f.Flag('+') {
+			fmt.Fprintf(f, ": %+v", e.Error)
+		} else {
+			fmt.Fprintf(f, ": %v", e.Error)
+		}
 	}
 	for _, tag := range e.Tags {
 		fmt.Fprintf(f, "\n\t%v = %v", tag.Key, tag.Value)