cmd/bench: run experiment benchmarks for both baseline and experiment gopls

Build baseline and experiment gopls within their respective directories and run experiment benchmarks using gopls_path flag.

Change-Id: Ifcc9aa9107257bac215361b71f87e419db339b97
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/461797
Run-TryBot: Dylan Le <dungtuanle@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
1 file changed