server: bark loudly if the test tenant cannot be created

For context, the automatic test tenant machinery is currently
dependent on a CCL enterprise license check.
(This is fundamentally not necessary - see cockroachdb#103772 - but
sadly this is the way it is for now)

Prior to this patch, if the user or a test selected the creation of a
test tenant, but the test code forgot to import the required CCL go
package, the framework would announce that "a test tenant was created"
but it was actually silently failing to do so.

This led to confusing investigations where a test tenant was expected,
a test was appearing to succeed, but with a release build the same
condition would fail.

This commit enhances the situation by ensuring we have clear logging
output when the test tenant cannot be created due to the missing
CCL import.

Release note: None

pkg/server/BUILD.bazel

@@ -306,6 +306,7 @@ go_library(
         "//pkg/util/log/eventpb",
         "//pkg/util/log/logcrash",
         "//pkg/util/log/logpb",
+        "//pkg/util/log/severity",
         "//pkg/util/metric",
         "//pkg/util/mon",
         "//pkg/util/netutil",

pkg/server/testserver.go

@@ -61,6 +61,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/admission"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
+	"github.com/cockroachdb/cockroach/pkg/util/log/severity"
 	"github.com/cockroachdb/cockroach/pkg/util/metric"
 	addrutil "github.com/cockroachdb/cockroach/pkg/util/netutil/addr"
 	"github.com/cockroachdb/cockroach/pkg/util/retry"
@@ -545,6 +546,7 @@ func (ts *TestServer) TestTenants() []serverutils.TestTenantInterface {
 func (ts *TestServer) maybeStartDefaultTestTenant(ctx context.Context) error {
 	clusterID := ts.sqlServer.execCfg.NodeInfo.LogicalClusterID
 	if err := base.CheckEnterpriseEnabled(ts.st, clusterID(), "SQL servers"); err != nil {
+		log.Shoutf(ctx, severity.ERROR, "test tenant requested by configuration, but code organization prevents start!\n%v", err)
 		// If not enterprise enabled, we won't be able to use SQL Servers so eat
 		// the error and return without creating/starting a SQL server.
 		ts.cfg.DisableDefaultTestTenant = true