dashboard: upsize freebsd-amd64-race builder to 16 vCPUs, 14.4 GB RAM

This is a followup to CL 214433. Start using n1-highcpu-16 machine type
instead of n1-highcpu-8 for the freebsd-amd64-race builder.

Increasing the RAM from 3.6 GB to 7.2 GB has helped golang/go#36444
significantly: the builder stopped failing consistently on x/tools
and resulted in many data races being uncovered in golang/go#36605.

However, by now, it has started to fail consistently again. This
time it seems to be due to low performance, causing the tests in
golang.org/x/tools/internal/lsp/regtest package to fail due with
"context deadline exceeded" errors.

FreeBSD is one of the ports that stays visible when "show only first-
class ports" is checked on build.golang.org. The other -race builders
have all been upgraded to the n1-highcpu-16 machine type by now out
of necessity.

It seems fair to provide the FreeBSD port with an equal amount of
resources, even if the increased memory isn't strictly required yet.
Once this change is applied, if the failures persist, we can be more
confident that the problem is due to the code or the port, rather
than due to this -race builder having 2𝗑 less CPU and RAM resources
compared to other -race builders.

An alternative is to increase timeout for this builder type, but I'm
opting to defer exploring that after equalizing the machine type.

For golang/go#36444.
For golang/go#34621.
For golang/go#29252.
For golang/go#33986.

Change-Id: I41f149365128c7bc6f576c778ac07618acc04612
Reviewed-on: https://go-review.googlesource.com/c/build/+/227859
Reviewed-by: Alexander Rakoczy <[email protected]>

Author: dmitshur

dashboard/builders.go

@@ -315,8 +315,8 @@ var Hosts = map[string]*HostConfig{
 	},
 	"host-freebsd-11_1-big": &HostConfig{
 		VMImage:            "freebsd-amd64-111-b",
-		Notes:              "Same as host-freebsd-11_1, but on n1-highcpu-8",
-		machineType:        "n1-highcpu-8", // 8 vCPUs, 7.2 GB mem
+		Notes:              "Same as host-freebsd-11_1, but on n1-highcpu-16",
+		machineType:        "n1-highcpu-16", // 16 vCPUs, 14.4 GB mem
 		buildletURLTmpl:    "https://storage.googleapis.com/$BUCKET/buildlet.freebsd-amd64",
 		goBootstrapURLTmpl: "https://storage.googleapis.com/$BUCKET/go1.4-freebsd-amd64.tar.gz",
 		env:                []string{"CC=clang"},