refactor: continue to simplify engine/netx (#769)

The objective of this diff is to simplify the code inside engine/netx
while moving more bits of code inside netxlite.

See https://github.com/ooni/probe/issues/2121

internal/engine/netx/resolver/bogon.go

@@ -1,32 +0,0 @@
-package resolver
-
-import (
-	"context"
-
-	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-// BogonResolver is a bogon aware resolver. When a bogon is encountered in
-// a reply, this resolver will return an error.
-//
-// Deprecation warning
-//
-// This resolver is deprecated. The right thing to do would be to check
-// for bogons right after a domain name resolution in the nettest.
-type BogonResolver struct {
-	model.Resolver
-}
-
-// LookupHost implements Resolver.LookupHost
-func (r BogonResolver) LookupHost(ctx context.Context, hostname string) ([]string, error) {
-	addrs, err := r.Resolver.LookupHost(ctx, hostname)
-	for _, addr := range addrs {
-		if netxlite.IsBogon(addr) {
-			return nil, netxlite.ErrDNSBogon
-		}
-	}
-	return addrs, err
-}
-
-var _ model.Resolver = BogonResolver{}

internal/engine/netx/resolver/bogon_test.go

@@ -1,37 +0,0 @@
-package resolver_test
-
-import (
-	"context"
-	"errors"
-	"testing"
-
-	"github.com/ooni/probe-cli/v3/internal/engine/netx/resolver"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
-)
-
-func TestBogonAwareResolverWithBogon(t *testing.T) {
-	r := resolver.BogonResolver{
-		Resolver: resolver.NewFakeResolverWithResult([]string{"127.0.0.1"}),
-	}
-	addrs, err := r.LookupHost(context.Background(), "dns.google.com")
-	if !errors.Is(err, netxlite.ErrDNSBogon) {
-		t.Fatal("not the error we expected")
-	}
-	if len(addrs) > 0 {
-		t.Fatal("expected to see nil here")
-	}
-}
-
-func TestBogonAwareResolverWithoutBogon(t *testing.T) {
-	orig := []string{"8.8.8.8"}
-	r := resolver.BogonResolver{
-		Resolver: resolver.NewFakeResolverWithResult(orig),
-	}
-	addrs, err := r.LookupHost(context.Background(), "dns.google.com")
-	if err != nil {
-		t.Fatal(err)
-	}
-	if len(addrs) != len(orig) || addrs[0] != orig[0] {
-		t.Fatal("not the error we expected")
-	}
-}