Enable the atomicalign, deepequalerrors, findcall, nilness,
reflectvaluecompare, sortslice, timeformat, and unusedwrite go vet
analyzers, which golangci-lint does not enable by default. Additionally,
enable new go vet analyzers by default as they become available.
The fieldalignment and shadow analyzers remain disabled because they
report so many errors that they should be fixed in a separate PR.
Note that the nilness analyzer appears to have found one very real bug
in tlsalpn.go.
## CI: restore load-generator run.
This restores running the `load-generator` during CI to make sure it doesn't bitrot. It was previously removed while we debugged the VA getting jammed up and not cleanly shutting down.
Since the global `pebble-challtestsrv` and the `load-generator`'s internal chall test srv will conflict this requires moving the `load-generator` run to the end of integration tests and updating `startservers.py` to allow the load gen integration test code to stop the `pebble-challtestsrv` before starting the `load-generator`.
The `load-generator` and associated config are updated to allow specifying bind addresses for the DNS interface of the internal challtestsrv. Multiple addresses are supported so that the `load-generator`'s chall test srv can listen on port DNS ports Boulder is configured to use. The `load-generator` config now accepts a `fakeDNS` parameter that can be used to specify the default IPv4 address returned by the `load-generator`'s DNS server for A queries.
## load-generator: support different challenges/strategies.
Updates the load-generator to support HTTP-01, DNS-01, and TLS-ALPN-01 challenge response servers. A new challenge selection configuration parameter (`ChallengeStrategy`) can be set to `"http-01"`, `"dns-01"`, or `"tls-alpn-01"` to solve only challenges of that type. Using `"random"` will let the load-generator choose a challenge type randomly.
Resolves https://github.com/letsencrypt/boulder/issues/3900
Aaron Gable
Jacob Hoffman-Andrews
Daniel McCarney