gopls: convert replay to use the new message types
gopls: convert replay to use the new message types

this save it from having to understand the json wire format.

Change-Id: I4261cb53a4d5fe2263d7d73ebf9e96e6be2e54a1
Reviewed-on: https://go-review.googlesource.com/c/tools/+/228720
Run-TryBot: Ian Cottrell <52376736e5e84615ec49f9c1843b8acc178b1d8d@google.com>
Reviewed-by: Peter Weinberger <dd140fb9530d791057dd8833ea6768ff65fcde71@google.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools