* cmd: update prometheus.NewProcessCollector args.
There's a new struct `prometheus.ProcessCollectorOpts` that is expected
to be used as the sole argument to `prometheus.NewProcessCollector`. We
don't need to specify `os.Getpid` as the `PidFn` of the struct because
the default is to assume `os.Getpid`. Similarly we don't need to set the
namespace to `""` explicitly, it is the default.
* SA: reimplement db metrics as custom collector.
The modern Prometheus golang API supports translating between legacy
metric sources on the fly with a custom collector. We can use this
approach to collect the metrics from `gorp.DbMap`'s via the `sql.DB`
type's `Stats` function and the returned `sql.DbStats` struct.
This is a cleaner solution overall (we can lose the DB metrics updating
go routine) and it avoids the need to use the now-removed `Set` method
of the `prometheus.Counter` type.
* test: Update CountHistogramSamples.
The `With` function of `prometheus.HistogramVec` types we tend to use as
the argument to `test.CountHistogramSamples` changed to return
a `prometheus.Observer`. Since we only use this function in test
contexts, and only with things that cast back to
a `prometheus.Histogram` we take that approach to fix the problem
without updating call-sites.
Now that Pebble has a `pebble-challtestsrv` we can remove the `challtestrv`
package and associated command from Boulder. I switched CI to use
`pebble-challtestsrv`. Notably this means that we have to add our expected mock
data using the HTTP management interface. The Boulder-tools images are
regenerated to include the `pebble-challtestsrv` command.
Using this approach also allows separating the TLS-ALPN-01 and HTTPS HTTP-01
challenges by binding each challenge type in the `pebble-challtestsrv` to
different interfaces both using the same VA
HTTPS port. Mock DNS directs the VA to the correct interface.
The load-generator command that was previously using the `challtestsrv` package
from Boulder is updated to use a vendored copy of the new
`github.org/letsencrypt/challtestsrv` package.
Vendored dependencies change in two ways:
1) Gomock is updated to the latest release (matching what the Bouldertools image
provides)
2) A couple of new subpackages in `golang.org/x/net/` are added by way of
transitive dependency through the challtestsrv package.
Unit tests are confirmed to pass for `gomock`:
```
~/go/src/github.com/golang/mock/gomock$ git log --pretty=format:'%h' -n 1
51421b9
~/go/src/github.com/golang/mock/gomock$ go test ./...
ok github.com/golang/mock/gomock 0.002s
? github.com/golang/mock/gomock/internal/mock_matcher [no test files]
```
For `/x/net` all tests pass except two `/x/net/icmp` `TestDiag.go` test cases
that we have agreed are OK to ignore.
Resolves https://github.com/letsencrypt/boulder/issues/3962 and
https://github.com/letsencrypt/boulder/issues/3951