va: log experiment results without base64 encoding

[jsha]

Go's JSON marshaling encodes []byte in base64. Previously, experiment results were logging *vapb.ValidationResult, which contained repeated corepb.ValidationRecord. In turn, corepb.ValidationRecord contains three []byte fields:

  repeated bytes addressesResolved = 3; // netip.Addr.MarshalText()
  bytes addressUsed = 4; // netip.Addr.MarshalText()
  repeated bytes addressesTried = 7; // netip.Addr.MarshalText()

By contrast, core.ValidationRecord (a non-protobuf struct), has fields of type netip.Addr:

	AddressesResolved []netip.Addr `json:"addressesResolved,omitempty"`
	AddressUsed       netip.Addr   `json:"addressUsed"`
	AddressesTried []netip.Addr `json:"addressesTried,omitempty"`

Those get serialized like 127.0.01, which is what we want.

This PR reworks the runExperiment function so that instead of receiving remoteResult (which could contain *vapb.IsCAAValidResponse or *vapb.ValidationResult), it receives a problem and an (optional) core.ValidationRecord. This allows us to more straightforwardly log things without running into base64-encoding problems.

To test this I modified TestExperimentalVAConcurrence to use HTTP-01 validation, since the affected log fields don't show up under DNS-01 validation. I also tweaked ipFakeDNS to allow customizing the IP address it returns.

Fixes #8701

[aarongable]

Remove debugging print

Suggested change

	b, _ := json.Marshal(logArgs)
	fmt.Println("oh no", string(b))

[aarongable]

You've deleted domain from all three test cases below.

[aarongable]

We have shorthand for this: mocklog.ExpectMatch().