Our current usage of WorkDone progress reporting (new in v3.15 of the
LSP spec) is in reporting progress on `go generate` commands. In
preparation for using this API more widely, factor out the reporting API
from the current io.WriteCloser wrapper (workDoneWriter).
Change-Id: Ib528093d81d4fc065528df90e100859e850b10df
Reviewed-on: https://go-review.googlesource.com/c/tools/+/229459
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
